The very first Sonic game for the Nintendo DS. Probably one of the most difficult Sonic games I have ever played.
I like Sonic Rush. It's probably one of my favorite Sonic games. There were some parts that gave me a lot of trouble though, especially Altitude Limit, the last special stage, and the final boss before the super Sonic fight (I had to switch to easy mode just to beat that boss). I actually kind of liked that it wasn't easy though, because it made it more satisfying when you won.
I also like Sonic Rush because of the music and because of Blaze the cat. She's one of my favorite Sonic characters.
Sonic Rush Adventure was good too in my opinion.