Candyshell is the best in my opinion as well !! I tried a lot of cases and its the best I found !
P.S: Incase slider is a great case but it scratches your iPhone
I like the really thin colored cases that they have out now for the 3G/3GS with a hole or cut-out where the Apple logo is so that it's clearly displayed. That way, I can show off my Apple pride!
For my 3G, I had an Incipio feather case that I really liked, so I'll probably get the iPhone 4 version of that when it's released as well.