Here's a list of robots I'd recommend looking at:
973 - Swerve drive, a unique intake system, a rotating tower shooter... I love 973's machine. From top to bottom, I love every part, and I wish I could take a close look at it myself.
67 - HOT did not fail in their long standing tradition of engineering kick-bot robots. The robot may not look terrifying, but their utility arm is a piece of engineering excellence, and they've put out an amazing robot without going overboard in anyway. They've also put together "on-the-fly" shifting without the need for pneumatics. An amazing robot all over.
48 - Delphi E.L.I.T.E.'s machines never fail to disappoint. The "Arm-ish" shooter on this robot gives it amazing scoring ability, as well as acting in several different tasks.
548 - One of the best non-traditional shooters this year. 548's arm sets them up for great lay-up shots, but now they've also added key shooting to their arsenal. This robot has several other design facets that I wish I could look at, mostly revolving around their arm and "shooter".
254 - "Skyfire", as it has been named, is a very well engineered robot. A simple drive system, simple arm, simple shooter, all combined into a great machine. They have also developed a "pop-up" drive system to help them get over the bump. The programming on this robot is also a marvel, having made ASTOUNDING use of the K'nect station.
971 - 971's "Renegade" machine is a mechanic marvel. Boasting a uniquely engineered tower and a lightening quick elevation system, I'd love to just spend a while taking the robot apart just to understand how everything goes together in there. Pay special attention to how the ball gets into the tower.
Those are the notable ones I'd recommend.
Other robots I'd recommend looking at: