Best-looking robot? Man, this is tough. In no particular order...
179's
2005 robot was great to see (unless you were against them, that is).
968's
robot this year stood out, even before it drove the score up thirty points. Sure, you could argue 254, but I think the red looked better on the field.
33 in
2005 was the most solid-looking robot I saw all season. It just looks so substantial on the field, you wonder how they ever made weight.
233 in
2006 and
2005 need no introduction.
If I can think of more, I'll edit or repost.