There's a game called "Bowmaster Prelude". I think it qualifies as Tower defense game. It's pretty awesome. ( http://armorgames.com/play/588/bowmaster-prelude )
They should make a genre for just tower defense games. I like Bloon TD3. there are some i can't stand though, i just never seem to get past the first or second level on some.
I too like Bloon Tower Defense 3 I also like the Demonic Defense series I don't know if that's in the same category or not but they are both kewl games