Of course many extremely clean (mostly powder-coated) robots come to mind when I saw this thread... Particularly ones made by 254, 233, 148, 118, 33, etc. I definitely think there is a lot of "taste" involved in this too, as 148 robots tend to look cool in a "transformers" sort of way with tons of edges and complexity. 254 robots tend to look more elegant and simple... even though they're really anything but simple. I love both those styles quite a bit, but I think I most love the robots that look like they have personality... that look like some little creature going about its business.
The one that stands out for me is 33's 2013 robot.
https://www.youtube.com/watch?v=2cgP2FJC7Hw It had all the elegance and polished aesthetics that 33's robots have had for quite a few years, but it also looked like a studious, efficient little creature in the way that Wally does, in my mind.
https://www.flickr.com/photos/danielernst/8586567293/
I think 1114's 2015 robot has to be the best-looking 2015 robot (in a year where most robots looked more like scaffolding or fork lifts than anything else)... The thing really looked like a weight-lifting crab (or something).