Overused. Smogon is terrible at tier balancing, though, and locks down Baton Pass stalls by restricting usage of key Pokemon on the same teams.
The best tier for stalling is Local Tournament formats (and you get the benefit of prizes).
Mega-Venasaur is a nasty Heal Tank.
Mega-Slowbro is great at setting up its defense without the fear of the lucky critical ignoring your buffs.
Scizor is great at balancing between healing and buffing, and can put out massive priority damage.
Mega-Sableye has decent base stats in Defense and Magic Bounce is a tank class all of its own.
LV 1 Sturdy Magnemite is a unique FEARmon that can really disrupt strategies of the opposition with either Toxic or Thunderwave builds. I know FEAR builds are frowned upon by "pros" but... If it works, who cares.
And of course, lesser tier tanks can fit into OU as well. Snorlax, Shuckle, Eelektross... in a tier dominated by speed and power, you can take full advantage of no speed investment to safely focus on damage output and sustainability.