NES.app lets you play Nintendo games on your iPhone. It is a fully functional, feature-rich Nintendo emulator.

Changes:

[nervegas] Tweaks to sound caching to get closer to real-time sync (you should be using auto-frameskip, slow frameskips will cause sound to loop)
[nervegas] Added zapper support (tap screen); works with: Duck Hunt, Hogan’s Alley, Wild Gunman, Gumshoe (game itself has glitches), Shooting Range, Gotcha! – Others do not yet seem to work

http://iphone.natetrue.com/nesapp/