WP Themes for developers (multiple sites/clients)

What do you do when you need to install a wordpress theme on a site that's going to end up in someone else's hands?

Stick to developer themes?

I'm looking for as many themes that that I can find which look nice (aren't plain, like Thesis) that I can build a site with and sell it, legally.

you don't want to get sued! so go and buy that theme