Well, I might as well post ALOT of robot master ideas anyone's alowed to use.
-Fire-
Thermite Man: Throws thermite.
Core Man: Able to create and withstand temperatures equal to that within the core of the sun.
Tempest Man: Able to cause firestorms.
-Water-
Tsunami Man: Able to cause large tsunamis.
Tide Woman: Built for underwater unarmed combat.
Geiser Man (or however that's spelled): Can create geisers.
-Electric-
Wire Man: Uses a wire for a whip, ala Indiana Jones.
Taze Man: Can use powerful taser.
Byte Man: Can edit space as if it was data.
Blitz Man: Can convert self into electricity to tackle opponents (like Heat Man).
-Space-
Meteor Man: Can call down meteors.
Lunar Woman: Built for space exploration.
Planet Man: Built to be able to explore any planet.
-Stone-
Mine Man: Built for mining.
-Explosive-
Trap Man: Lays mines.
Frag Man: Throws frag grenades.
Missile Woman: Launches very fast missiles.
Nuke Man: Created to be able to destroy large areas quickly
-Other-
Build Man: Built for construction, has construction crane for arm.
Coin Man: Built for banking, can launch coins at lethal speeds.
Steam Man: Can utilize powerful spouts of steam.
Moment Man: Can stop time to carefully analize enemies and situations. Sort of a robot detective.
Turrent Man: Can deploy turrents.
Change Man: Can change affinity.
Whatever Man: Doesn't really do anything.
Sniper Man: Sniper Robot.
If anyone has already come up with one of these concepts, whatever.
Feel free to use any of them, just make sure to give me a little credit.