Well, it's as the title says. I don't know if this will work in either iPhone 2G/3G/3GS, but at least it works for iPod Touch 3G, OS 3.12.
First Step: Jailbreaking
For OS 3.12 (and all other firmwares), you need to jailbreak it first. You can use blackra1n. The rest are self-explaining, but I'll post the steps here anyway:
1. Download blackra1n from here.
2. Terminate processes related to iTunes (iTunes.exe and iTunesHelper.exe)
3. Connect your iPod to your computer.
4. Run blackra1n.
5. Click on "make it ra1n", don't panic if it doesn't work for the first time; Exit the program and run it again.
6. When it succeed, there will be a confirmation to restart your iPod. Click OK and your iPod will restart.
7. Then you will see a picture (the same) again on your iPod. Exit blackra1n and run it again once. When the confirmation to restart your iPod appears, your iPod will return to home screen.
8. Congrats, you have succeed in jailbreaking your iPod!
NB: For OS 3.12, iPod jailbreaking is still in tethered mode. It means if you let your iPod battery out or shut down or restart, you have to restart jailbreaking again.
Second Step: Inserting the Cracked Game
OK, you have finished jailbreaking your iPod. Now is the real deal, inserting the game!
1. Download "Cydia" from "blackra1n" (it should appear in your home screen when you successfully jaibreak your iPod)(Need Wi-Fi).
2. Download "afc2add" from "Cydia" (Need Wi-Fi).
3. Download this app from Mr. Rizwan (thanks Mr. Rizwan!).
4. Extract the files, then run “Patch_App31.bat” while connecting your iPod to the computer.
5. Go search cracked .ipa files in the internet and open it with iTunes (Don't ask me where to get it, just google).
6. Sync with your iPod and go games like mad!
That's another tutorial from me, hope that helps!
First Step: Jailbreaking
For OS 3.12 (and all other firmwares), you need to jailbreak it first. You can use blackra1n. The rest are self-explaining, but I'll post the steps here anyway:
1. Download blackra1n from here.
2. Terminate processes related to iTunes (iTunes.exe and iTunesHelper.exe)
3. Connect your iPod to your computer.
4. Run blackra1n.
5. Click on "make it ra1n", don't panic if it doesn't work for the first time; Exit the program and run it again.
6. When it succeed, there will be a confirmation to restart your iPod. Click OK and your iPod will restart.
7. Then you will see a picture (the same) again on your iPod. Exit blackra1n and run it again once. When the confirmation to restart your iPod appears, your iPod will return to home screen.
8. Congrats, you have succeed in jailbreaking your iPod!
NB: For OS 3.12, iPod jailbreaking is still in tethered mode. It means if you let your iPod battery out or shut down or restart, you have to restart jailbreaking again.
Second Step: Inserting the Cracked Game
OK, you have finished jailbreaking your iPod. Now is the real deal, inserting the game!
1. Download "Cydia" from "blackra1n" (it should appear in your home screen when you successfully jaibreak your iPod)(Need Wi-Fi).
2. Download "afc2add" from "Cydia" (Need Wi-Fi).
3. Download this app from Mr. Rizwan (thanks Mr. Rizwan!).
4. Extract the files, then run “Patch_App31.bat” while connecting your iPod to the computer.
5. Go search cracked .ipa files in the internet and open it with iTunes (Don't ask me where to get it, just google).
6. Sync with your iPod and go games like mad!
That's another tutorial from me, hope that helps!