Some honorable mentions have to be the robots below. You can take one look at the paint and know which team you are looking at because these teams have built that brand that most people recognize.
148 Raptor in 2011
https://www.youtube.com/watch?v=XECmOwmYiu8
I think I saw someone mention this already and I agree. Their mastery of sheet metal components and the fact that it can be any color as long as it is black make all of their machines simply awesome to look at. This robot stuck out to me as way above the bar for sheet metal robots.
254 Barrage in 2014
https://www.youtube.com/watch?v=aFZy8iibMD0
What I love about the 254 machines is that they are not the most complicated or crazy looking. Their machines are simple, clever, and elegant with not a single motion or pound wasted. From an engineering standpoint, the quality and performance of their robots stand above the rest. Simple lines and popping blue paint let you know which team is on the field before the robot even moves. As soon as their robots move on the field your eye is drawn to them and you have no doubt 254 is on the field.
Cool robots are not the most complicated or best looking, cool robots are the ones that win. This is why this robot ranks one of the coolest on my list of favorites even if it is not eye candy for everyone else.