You can have only TWO Robo sets for the rest of your life, no matter what CR game you play... What sets would you have?
Ray Sky
Glider Gun
Burrow Bomb D
Wall Pod
Plus One Legs
Comet
Needle Gun
Burrow Bomb D
Wall Pod
Short Thrust Legs
Ray Sky is my most effective combat wise, and covers both long and mid-range arenas. Comet covers close quarters and lava arenas, along with anything slanted (though maybe not very effectively), and arenas with tall pillars. They are both very fun to play with, even if Comet isn't that great.