Don't know if this has been mentioned yet, but scarf hydreigon is boss. As a late game sweeper, you make sure all pokemon are at least neutral to one of it's moves and you spam that with a modest nature, maxed out sp attack, and hopefully STAB move. Nuff said.
i dunno... if you're running scarf, i like my haxorus better.
can come in on dragonite using DDance, and still outspeeds and OHKO's with outrage (i know, locked in, but even if you switch to a steel, you still lose a good chunk of health)
it can take out rotom/gengar with earthquake thanks to mold breaker.
i also have it carry x-scissor and brick break.
other fun options it can carry are dragon claw, dual chop, night slash, rock slide, and shadow claw.
of those, i'd have to run a calc to see if dual chop/dragon claw one shot a marvel scale dragonite, but i think it's pretty good with that set.
sure, you have a reasonable chance to win on speed unless you really don't invest in speed, but the only real use i got from scarfed hydreigon was that it wasn't expected to outspeed latios, so i could get off draco meteor/dragon pulse/dark pulse (depending on which set i was using and my mood/memory of the remaining opponents)
it's good, but try scarfing a haxorus in its place and see how you feel with that.