"Atomic Fart" sounded good. It has thirty fart sounds and a "drum set" mode where you can play five different fart sounds without scrolling through the list.
I thought I had another innovative far app idea the other day: Fart competition app (Friend Fart Off) or a fart analysis and rating app (with real audio analysis) . Unfortunately after a few Google/App Store searches I found a few developers have already innovated in this area. Bummer.
A finite set is so limiting. I'm waiting until someone maps the universe of possible farts onto a continuous, multi-dimensional parameter space that I can navigate by X & Y coordinates of where I touch combined with gyroscope, accelerometer, & compass. I guess I'll have to switch to Android.
And GPS. If I'm in France, I want my farts to sound French (you can't pass an American fart off as a European fart. I haven't tried, but it's a well respected opinion in my mind). If I'm in Antarctica, I want them to sound like the cheeks were shivering.