I'm still working out the kinks around EVs, but here is a good Rotom for a Hail Team, where Blizzard's perfect accuracy and synergy with Electric attacks works very well. Where Froslass gets STAB on Blizzard, Rotom retains the fighting immunity without compouding weaknesses to Fire, and, as a bonus, it resists Steel making it a good answer to Metagross. Also helps out Starein with an Electric resistance, and Abomasnow with a Bug resistance.
Rotom-Fridge @ Leftovers
Nature: Bold
Trait: Levitate
EVs: 252 HP/120 Def/88 Spe/48 SDef
~ Blizzard
~ Charge Beam
~ Rest
~ Sleep Talk
Alright, so the deal here is Fridge Rotom is pretty much Spiritomb's equal in defensive power. The 88 Speed allows you to outspeed Scizor, and with high HP.Defense investment, Bullet Punch is rendered ineffective. Otherwise this is basically the Regice set put on Rotom, the idea being to use Charge Beam to increase SA while tanking off damage. With perfect accuracy in Hail, Blizzard becomes quite lethal after an SA Boost.
Rotom-Fridge @ Leftovers
Nature: Bold
Trait: Levitate
EVs: 252 HP/120 Def/88 Spe/48 SDef
~ Blizzard
~ Charge Beam
~ Rest
~ Sleep Talk
Alright, so the deal here is Fridge Rotom is pretty much Spiritomb's equal in defensive power. The 88 Speed allows you to outspeed Scizor, and with high HP.Defense investment, Bullet Punch is rendered ineffective. Otherwise this is basically the Regice set put on Rotom, the idea being to use Charge Beam to increase SA while tanking off damage. With perfect accuracy in Hail, Blizzard becomes quite lethal after an SA Boost.