This is a compilation of cheat codes I made for various games. I made these myself, these were not taken from anywhere else. These codes typically are not your run of the mill cheats that you find everywhere. Also these all work, unlike many codes on the internet that just plain don't work. Game Genie codes are used when possible, but I might have some Pro Action Replay ones. I try to make clear which version is used. I've had many of these for awhile and wanted to compile and share them.

Game Title  System & Version
Castlevania NES, US PRG1
Contra III: The Alien Wars SNES, US
Fester's Quest NES, US
Final Fantasy IV SNES, JP J2E v3.21
Gradius III SNES, US
Holy Diver NES, JP
Mega Man X SNES, US V1.1
Ninja Gaiden NES, US
Ninja Gaiden II NES, US
Ninja Gaiden III NES, US
Pokemon Blue&Red GB, US
Star Wars Empire Strikes Back NES, US
Teenage Mutant Ninja Turtles NES, US
Top Gun NES, US


Castlevania US PRG1 Code
Don't fall backward when hit.
AEKPYVPA
Don't lose life when hit. ATSVPYST


Contra III: The Alien Wars Code
30 Lives Code. In the options menu you will be able to set your Extra Lives count to 30.
D784-A7D4
D087-AFA4
Don't lose weapons when you die. 64BA-64D1
64B8-64A1


Fester's Quest US Code
Shots go through walls. They don't disappear on contacting a wall.
OXATVE
AEATNA
Blobs have less health. The blobs you find on the street don't take 8 hits to kill anymore. PASAGIYA


Final Fantasy IV JP J2E v3.21 Code
1.5 Million Experience Points per battle.
FD38-D4DE
Walk anywhere on Overworld. Through mountains or over water, nothing stops you. 6DCF-D7D7
Walk anywhere in towns and dungeons. Beware walking over chests and pots will warp you. CBC2-04A4
CBCA-0DD4
CBCC-0F04
CBC6-0464
Combine any items. While this code is enabled, if you move an item in your inventory onto another it will add its quantity to the item you placed it on. For example buy 99 of a cheap item and then move it to place it where you have 1 of a good item like a HiPotion. The 99 cheap items disappear but you have 99 more HiPotions. Experiment to understand better. 6DC3-ADD0


Gradius III US Code
Use the Up,Up,Down,Down,L,R,L,R,B,A full powerup code infinitely.
D4A9-0D0D




Holy Diver JP Code
Don't take damage from objects. Lava or other background features may still kill you.
SXYYNE
Magic use unlimited.
AVGSSI


Mega Man X US V1.1 Code
No Dash Upgrade Capsule. Play through the game without getting any upgrades. 3CAA-CDB3
3CAA-CD23
No Zero Buster Upgrade. Combine with above code to challenge yourself with no upgrades. The game can be beaten without any of them. 6D20-343F
Use Hadoken fireball anytime. Without full energy, without all upgrades. Destroy your enemies. Note if you don't have the armor upgrades the animation for doing the hadeoken isn't there but it still works. 3CCE-4460
3CCE-44A0
3CCD-1DA0
3CCD-1FD0
Start with all armor upgrades. Start with Head, Leg, Body, and Arm Cannon Upgrades. No Hadoken. DEBE-446F
BBBE-47DF
6DBD-1FDF
 Note: These codes may work on version 1.0 and also the Japanese versions.


Ninja Gaiden US Code
Level Select. This game has a hidden level select that can be accessed with this code. Hold A and use the dpad to change level. Press start to begin. AZZTTI
OTZTYS
EGZVAI



Ninja Gaiden II US Code
Level Select. This game has a hidden level select that can be accessed with this code. Hold A and use the dpad to change level. Press start to begin. AZUGVSGZ
YLUGNSNY
KIUKESNN



Ninja Gaiden III US Code
Debug Mode. This game has a hidden debug feature that has a level select and if you pause the game and press select you can toggle invulnerability. And the Game Genie code is easy to remember. Again hold A and use the dpad to change level. AUYNOY



Pokemon Blue (and maybe Red) US Code
Walk through walls. Walk through whatever you want. Beware walking into undefined areas will crash the game. 00C-23F-F7A
Reverse item loss. When you use or otherwise lose an item instead you gain an extra one. For example if you have a Masterball and Toss it or use it to capture something you will end up with both the one you used plus one more. If you toss an item, for every one you toss instead you gain. This can be used in combination with the following code. 83E-86B-A24
Item loss instead changes item type. Example: Use or toss 1x Pokeball and instead of losing 1x Pokeball the item slot that was Pokeballs will change by however much the count was to decrease by or to increase by if using the above code in combination with this. Be careful to know what item you want to transform into another. If you create an item that cannot be thrown away you may get stuck with it. So save before modifying anything and only save again afterwards if everything goes well. The easiest thing to do is to change Pokeballs into Masterballs. Item Numbers 00E-75B-6E6
Be able to Toss almost anything. If you through cheating have ended up with an item you cannot toss but don't want or shouldn't have you can enable these codes and it will override the check that prevents you from tossing "important" items like Oak's Parcel. 937-6A9-A2C
007-6B9-D55
Oak's Pokeball Modifiers. These codes change the Pokemon inside the 3 Pokeballs you can choose from at the beginning of the game. Replace xx with the number of the Pokemon species you want. The first code is the ball on the left, next the middle, and last is the ball on the right. Species Numbers xx1-0EA-2A8
xx1-1FA-2AC
xx1-30A-80C
Wild Pokemon Encounter Modifer. Using these codes and replacing xx with the species number of any Pokemon will force any wild pokemon encounter to be the chosen species. However their graphics during the battle will be glitched due to limitations of the Game Genie. The Pokemon will behave normally and can be captured and won't suffer any graphics problems once caught. Species Numbers 3E8-ED8-4C1
xx8-EE8-A2C
008-EF8-D55


Star Wars Empire Strikes Back Code
Normal Blaster does insane damage. OVKONNOX
Unlimited Force Power. As long as you have some Force Power, you can use your powers with no limit as they use no energy. PXOPVTVK


Teenage Mutant Ninja Turtles US Code
Always get critical health damage boost. In TMNT you get a boost to your damage when your health is low. With this code you get this boost even at full health. OXEOVOOU
AOEONPYY
XVOPEPAE
Tough Turtles. Reduces most damage to a very small amount. OXKPXEPV
TUKPUAGA



Top Gun US Code
Enable music on take off. For some reason the flight music only plays when the computer demo runs. This alters the game so it will play music while you play the game, unless you die and respawn.  AAPVKA
... ...




Pokemon Red/Blue Monster Species Numbers
01 Rydon    
02 Kangaskahn   
03 Nidoran M    
04 Clefairy   
05 Spearow   
06 Voltorb   
07 Nidoking   
08 Slowbro   
09 Ivysaur   
0A Eggecutor   
0B Licktung   
0C Exegute   
0D Grimer   
0E Gengar   
0F Nidoran F    
10 Nidoqueen   
11 Cubone   
12 Ryhorn   
13 Lapras   
14 Arcanine   
15 Mew       
16 Gyrados   
17 Shellder   
18 Tentacool   
19 Gastly    
1A Scyther   
1B Staryu   
1C Blastoice   
1D Pinser   
1E Tangala   
21 Growlithe   
22 Onix       
23 Fearow   
24 Pidgey   
25 Slowpoke   
26 Kadabra   
27 Graveler   
28 Chansey   
29 Machoke   
2A Mr. Mime   
2B Hitmonlee   
2C Hitmonchan   
2D Arbok    
2E Parasect    
2F Psyduck   
30 Drowzee   
31 Golom    
33 Magmar   
35 Electabuzz   
36 Magneton   
37 Koffing   
39 Mankey   
3A Seel       
3B Digglett   
3C Tarous   
40 FarFetche'd   
41 Venonat   
42 Dragonite   
46 Doduo    
47 Poliwag   
48 Jynx       
49 Moltres   
4A Articuno   
4B Zapdos    
4C Ditto      
4D Meowth   
4E Krabby   
52 Vulpix     
53 Ninetails   
54 Pikachu   
55 Raichu   
58 Dratini    
59 Dragonair   
5A Kabuto   
5B Kabutops   
5C Horsea   
5D Seadra   
60 Sandshrew   
61 Sandslash   
62 Omanyte   
63 Omaster   
64 Jigglypuff   
65 Wigglytuff   
66 Eevee     
67 Flareon   
68 Jolteon   
69 Vaporeon   
6A Machop   
6B Zubat     
6C Ekans   
6D Paras    
6E Poliwhirl     
6F Poliwrath   
70 Weedle   
71 Kakuna   
72 Beedril   
74 Dodrio    
75 Primeape   
76 Dugtrio   
77 Venomoth   
78 Dewgong   
7B Caterpie   
7C Metapod   
7D Butterfree   
7E Machamp   
80 Golduck   
81 Hypno    
82 Golbat    
83 Mewtwo   
84 Snorlax   
85 Magikarp   
88 Muk        
8A Kingler   
8B Cloyster   
8D Electrode   
8E Clefable   
8F Weezing   
90 Persian   
91 Marowak   
93 Haunter   
94 Abra       
95 Alakazzam   
96 Pidgeotto   
97 Pidgeot   
98 Starmie   
99 Bulbasaur   
9A Venusaur   
9B Tentacruel   
9D Goldeen   
9E Seaking   
A3 Ponyta   
A4 Rapidash   
A5 Rattata   
A6 Ratticate   
A7 Nidorino   
A8 Nidorina   
A9 Geodude   
AA Porygon    
AB Areodactyl   
AD Magnemite    
B0 Charmander    
B1 Squirtle   
B2 Charmeleon   
B3 Wartortle   
B4 Charizard   
B9 Oddish   
BA Gloom   
BB Vileplume   
BC Bellsprout   
BD Weepinbell   
BE Victreebell   


Item Numbers
01=MASTER BALL       - $0
02=ULTRA BALL          - $1200
03=GREAT BALL          - $600
04=POKéBALL             - $200
05=TOWN MAP            - $0
06=BICYCLE                - $0
07=?????                     - $0
08=SAFARI BALL          - $1000
09=POKéDEX               - $0
0A=MOON STONE        - $0
0B=ANTIDOTE              - $100
0C=BURN HEAL           - $250
0D=ICE HEAL               - $
0E=AWAKENING          - $
0F=PARLYZ HEAL        - $
10=FULL RESTORE     - $
11=MAX POTION          - $
12=HYPER POTION     - $
13=SUPER POTION     - $
14=POTION                  - $
15=BOULBERBADGE  - $0
16=CASCADEBADGE   - $0
17=THUNDEBADGE    - $0
18=RAINBOWBADGE  - $0
19=SOULBADGE         - $0
1A=MARSHBADGE      - $0
1B=VOLCANOBADGE  - $0
1C=EARTHBADGE       - $0
1D=ESCAPE ROPE      - $
1E=REPEL                   - $
1F=OLD AMBER          - $0
20=FIRE SOTNE          - $2100
21=THUNDER STONE - $2100
22=WATER STONE      - $2100
23=HP UP                    - $9800
24=PROTEIN                - $9800
25=IRON                      - $9800
26=CARBOS                 - $9800
27=CALCIUM                - $9800
28=RARE CANDY         - $4800
29=DOME FOSSIL        - $0
2A=HELIX FOSSIL        - $0
2B=SECRET KEY         - $0
2C=?????                     - $0
2D=BIKE VOUCHER     - $0
2E=X ACCURACY         - $950
2F=LEAF STONE          - $2100
30=CARD KEY             - $0
31=NUGGET                - $10000
32=PP UP                    - $0
33=POKé DOLL           - $1000
34=FULL HEAL            - $600
35=REVIVE                  - $1500
36=MAX REVIVE          - $4000
37=GUARD SPEC.       - $700
38=SUPER REPEL      - $500
39=MAX REPEL           - $700
3A=DIRE HIT                - $650
3B=COIN                      - $10
3C=FRESH WATER      - $200
3D=SODA POP             - $300
3E=LEMONADE           - $350
3F=S.S TICKET            - $0
40=GOLD TEETH         - $0
41=X ATTACK               - $500
42=X DEFEND             - $550
43=X SPEED                - $350
44=X SPECIAL             - $350
45=COIN CASE            - $0
46=OAK'S PARCEL      - $0
47=ITEMFINDER         - $0
48=SILPH SCOPE        - $0
49=POKé FLUTE         - $0
4A=LIFT KEY               - $0
4B=EXP.ALL                - $0
4C=OLD ROD              - $0
4D=GOOD ROD           - $0
4E=SUPER ROD         - $0
4F=PP UP                   - $0
50=ETHER                  - $0
51=MAX ETHER          - $0
52=ELIXER                 - $0
53=MAX ELIXER         - $0
 
54 - C3=NOTHING

C4=HM01 - CUT  
C5=HM02 - FLY
C6=HM03 - SURF
C7=HM04 - STRENGTH
C8=HM05 - FLASH
C9=TM01 - MEGA PUNCH
CA=TM02 - RAZOR WIND
CB=TM03 - SWORDS DANCE
CC=TM04 - WHIRLWIND
CD=TM05 - MEGA KICK  
CE=TM06 - TOXIC 
CF=TM07 - HORN DRILL  
D0=TM08 - BODY SLAM
D1=TM09 - TAKE DOWN
D2=TM10 - DOUBLE-EDGE
D3=TM11 - BUBBLEBEAM
D4=TM12 - WATER GUN
D5=TM13 - ICE BEAM
D6=TM14 - BLIZZARD
D7=TM15 - HYPER BEAM
D8=TM16 - PAY DAY
D9=TM17 - SUBMISSION
DA=TM18 - COUNTER
DB=TM19 - SEISMIC TOSS
DC=TM20 - RAGE   
DD=TM21 - MEGA DRAIN 
DE=TM22 - SOLAR BEAM
DF=TM23 - DRAGON RAGE
E0=TM24 - THUNDERBOLT
E1=TM25 - THUNDER
E2=TM26 - EARTHQUAKE
E3=TM27 - FISSURE
E4=TM28 - DIG  
E5=TM29 - PSYCHIC
E6=TM30 - TELEPORT
E7=TM31 - MIMIC
E8=TM32 - DOUBLE TEAM
E9=TM33 - REFLECT
EA=TM34 - BIDE
EB=TM35 - METRONOME
EC=TM36 - SELFDESTRUCT
ED=TM37 - EGG BOMB
EE=TM38 - FIRE BLAST
EF=TM39 - SWIFT
F0=TM40 - SKULL BASH
F1=TM41 - SOFTBOILED
F2=TM42 - DREAM EATER
F3=TM43 - SKY ATTACK
F4=TM44 - REST
F5=TM45 - THUNDER WAVE
F6=TM46 - PSYWAVE
F7=TM47 - EXPLOSION
F8=TM48 - ROCK SLIDE
F9=TM49 - TRI ATTACK
FA=TM50 - SUBSTITUTE
FB=TM51 - CUT
FC=TM52 - FLY
FD=TM53 - SURF
FE=TM54 - STRENGH
FF=TM55 - FLASH