Might as well keep adding variety here.
Suggesting an underused, underrated, and very good offensive force.
Muk
 
@Choice Band
Adamant
252 HP / 252 Atk / 4 Spe
Sticky Hold
Gunk Shot
Focus Punch
Shadow Sneak
Fire Punch
Armed with incredible bulk, immense power, and undeniable "cool factor", Muk is a great teammate for Meganium.
While it might not provide quite as good type synergy as Qwilfish, Muk can still easily take advantage of the Bug and Poison attacks aimed at Meganium. Unlike Qwilfish, Muk can actually take a special attack or 5 and hit back. The ability to protect the team from Toxic Spikes is always a plus too.
With max HP investment and respectable base defenses, Muk really can shrug off quite a few attacks. With Choice Band boosted power, he can destroy unsuspecting teams. Fire Punch is arguably better than Ice Punch now that Gligar and Claydol are gone to reliably hit some bug- and steel-types. Shadow Sneak is great as emergency priority and wrecks offensive Rotom. Choice Band Focus Punch is for smashing Steel- and Rock- types trying to switch in and take Gunk Shot.
Gunk Shot is powerful. It OHKOs almost anything that doesn't resist Poison. With the threat of a possible Focus Punch, Aggron and Magnezone are much less inclined to switch in. Steelix, Qwilfish, and bulky ghosts are pretty much the only completely safe switch ins.