I've been a fan of 2826's aesthetics the past few years. I really liked the industrial, bare metal look they had this year. IMO a robot's performance on the field contributes to its aesthetics as well, and Wave definitely wasn't lacking in that regard.
http://tinyurl.com/jvg7ofu
I'll also contribute the obvious numbers one, one, and eight. They make some of my favorite looking robots year in and year out.
http://tinyurl.com/o5jyly7