I think this is my favorite Rotom form, because it's kinda like Lanturn with only one weakness, thanks to Levitate.
Item: Damp Rock
Rain Dance: this will set up...
Thunder + Hydro Pump: Both powerful STAB moves boosted by Rain Dance.
Signal Beam: Still gotta deal with those Grass-types, and this is Rotom's only super effective move against them. It's pretty good, all things considered. Decent power, plus can cause Confusion? Sounds good to me!