So i was looking at the klefki (his name is dovahkin in case you were wondering) i caught a few days ago, and noticed it had a calm nature. I think with with the proper EV spread, leftovers, and that delicious priority dualscreens It should be able to take quite a beating. Throw in priority thundershock and foulplay for some damage, and it should be able to take out even the dreaded megachomp and talonflame.
Edit:
http://replay.pokemonshowdown.com/oubeta-70095956
First test run with 220 Health, 220 Def, 38 S.Def, spread seems to have gone well. Managed to 1HKO Aegislash in the first 2 turns with foulplay after setting up reflect and effectively ignoring the pittance of damage it dealt thanks to leftovers. After that, with the help of some INCREDIBLE luck regarding thundershock, i was able to decimate MegaKangaskhan's health with only a dent in Klefki's health to show for it. I think Klefki would have died in 2-3 turns if not for static, but even in that case it managed to take a sizable chunk of health off MegaKhan in only 2 moves.
Over all seems promising but one sample does not a test make, so back to the ol' grind.
Round 2
http://replay.pokemonshowdown.com/oubeta-70101369
Things are still looking up for the Dohvahkin. This match started off against a Megalucario, which being a fighting/steel type is a bit of an even type match up for most Klefki, but for this set up is kinda shitty since its only attack is Dark type, but The DovahKin will not be deterred. Round 1 starts with with the opponent, feeling safe in the knowledge that no mere Klefki's meager attack stats and limited attack move pool could not hope to even dent his mighty Megalucario, boosting himself with sword dance. Unfortunately for him this is no mere Kelfki, this is The Dohvakin he's messing with, and a x2 427 Atk foulplay is going to hit like a GOD. DAMN. TRUCK. Even against Megalucario.
Next round goes a little differently than I expected, with Lucario immediately springing into a Close Combat, but Klefki was able to tank the hit like a boss thanks to glorious nippon steel Reflect damage reduction. Now comes turn 3 and, due to static on Lucario, Klefki gets to go first barreling along in that truck I was talking about earlier, and on top of all that "Lucario is paralyzed and unable to move." Turn 4 and Lucario is now thoroughly doomed, thanks to static. Realizing his last hope of victory, Lucario uses Extreme Speed to try and last hit Klefki with a priority move, unfortunately for him Klefki gives no fucks and that spells the end for Megalucario.
SHARP LIKE KATANA. METAL FOLDED OVER 1000 TIMES. CAN CUT THROUGH ANYTHING. GAINJIN GO HOME.[/spoiler]