Swampert most definitely.
Awesome typing. Awesome defenses. Awesome support moves.
And it can come in late-game to tank against some top threats like Heatran.
Love it.
At the moment, I'm rotating 3 leads:
Anti-lead Weavile:
Fake Out,
Taunt,
Night Slash,
Counter.
It works wonderfully well. It completely counters Azelf lead, without letting it set up Stealth Rock, It kills off Anti-Lead Starmie, Fake out breaks most sashes, which is useful, when i'm not setting up my own SR. Counter is a great move in itself, taunt a Leadpert into attacking, generally using their superior Attack, only for Weavile to survive, and throw it back in their face for a swift OHKO.
It also works against cocky Metagross leads, who think they can kill you off promptly, with Meteor Mash, or Bullet Punch.
Bronzong's Gyro Ball does enough to provide a Countered OHKO as well, it really works wonders. The only thing Really capable of outdoing it is Jirachi, if it gets a flinch, and Aerodactyll.
Who needs the first turn flinch when you outspeed your opponents? pokemon that you use counter against, usually don't have focus sash (Metagross, Bronzong, Swampert). Ice Shard doesn't need to be a OHKO because Aero has sash anyway.But then you don't get the first turn flinch, which is primarily why it gets used. And since Weavile needs a boost to OHKO with Ice shard, it would still lose out.
I was running Jolly Focus Sash Mamoswime for a long while. Endeavor/Earthquake/Ice Shard/Stealth Rock. He has his way with most leads, but the fact that he couldn't beat Azelf/Fake Out Pokemon lead me to use..
I believe it's called "prediction". You predict if said Azelf is gonna dare use SR against you or just plain attack you. I rather have the ability to beat Aero and Yanmega leads and provide a nice check against dragons if I manage to keep Weavile for later in the game.
And if you predict wrong? You've just wasted a Pokemon slot. Leadvile doesn't intend on returning later on, hence Sash + Counter. It's designed purely to counter most common leads, and then be used as a sacrifice to get your scout/wallbreaker in.
Actually if you use Bite, you can beat Azelf if you go Adamant
Aero runs a focus sash, though. The one thing about that set, is that I tend to see the majority of Weaviles running Ice Punch over Night Slash for that very reason (and for revenge killing dragons).Who needs the first turn flinch when you outspeed your opponents? pokemon that you use counter against, usually don't have focus sash (Metagross, Bronzong, Swampert). Ice Shard doesn't need to be a OHKO because Aero has sash anyway.