No chaos drives, since they're in the G.U.N. robots.
I don't like the small animals because in the 2D Sonic games they just run off (in Marble Zone straight into the lava >_>) and in the 3D games I prefer chaos drives for Chao raising since they don't have these annoying parts. And if you do want to style your Chao, you are better off looking for the animals hiding in the stages. Argh! I'm chaoing again! *slaps*
I like the flowers best. They mark your victory and stay in the Zone until you finish it. And if you run past them you feel like you've actually done something. Or not.