[Ernesto]

While you're right that the electric appliances are at an awesome Speed tier for UU, and it's an awesome revenge killer under Hail, I wouldn't mention revenging Heracross as a useful trait on it, it's way too situational:
252 SpA Rotom-F Blizzard vs. 0 HP / 0 SpD Heracross: 177-208 (58.8 - 69.1%) -- guaranteed 2HKO after Stealth Rock and weather
In return, Heracross only needs SR (and not being locked into Earthquake / Aerial Ace)
252 Atk Heracross Megahorn vs. 0 HP / 4 Def Rotom-F: 180-213 (74.68 - 88.38%) -- 93.75% chance to OHKO after Stealth Rock

So essentially, Rotom-F needs Heracross to have switched into SR twice and have taken two rounds of Hail damage to be OHKOed or have been hit, which doesn't usually happen if Hera's played well. In return, Heracross beats it with its 3 standard moves, assuming they hit.

That said, any Scarf Rotom is awesome, so I won't question it being the first set, lol

EDIT: Never mind, it revenges Hera if 'ts locked into Close Combat. It's still a little situational—since Hera at -1,-1 will probably switch out for fear of being killed, unless something else can take advantage of the switch—but rather effective either way. Choice Scarf as number one set is perfectly fina