I've built my full team for competitive single battles, and have messed around before on simulators with great results. Some megas can be extremely OP (with the likes of Mega Gengar and Mega Kanghaskhan being banned to ubers by Smogon), even in the OU category (Mega Lucario is an absolute machine in the right hands).

Aegislash has pretty much been figured out by now, with moves such as Earthquake and Sucker Punch not triggering King's Shield. It's still a decent pivot, though.

As for defog, I love it when I know my opponent has it. I send in my bisharp with Defiant, getting a free swords dance on the switch and proceed to anihalate some souls.

Weather nerf has changed a lot about team building. The current metagame seems centralized a lot on physical moves and priority (Gale Wings Talonflame... Urgh...)