Play blind - ECHO forces you to play with your sense of hearing only. An audial space game, with no controls other but tilting your device.
Survive as long as you can to join the top list on Game Center.
The fact I could easily create all the -sd/-hd/-ipad/-padhd version based on the highest resolution made it really easy and quick to add/change some sprite grafics.
Automatic resizing and generation of the different sheets, also packing/conversion.
I am using Box2d for pixelperfect collisions. Each sprite has a shape, the GB2ShapeCache is also a huge help and removed a lot of hassle, it allowed me to focus on my game - not on Box2d.
Circleshapes ;-) Most of my sprites are round, haha.