Be nice. Or else.
StudioPress makes some pretty nice ones on their Genesis framework: http://www.studiopress.com/
Keep in mind, it is a framework, so it's going to be more bloated than themes that do not have as many dependencies or child / parent relationships. All in all, I like these a lot and have used them for years. Performance has come a long way and they have a lot of very nice features.
Sweet, I'll check these out.