Bibarel
Item : Lucky Egg is best overall but you can use different items.
Ability : Simple is best in Platinum, but anything can work in Diamond and Pearl.
-Yawn / Thunder Wave / Pluck / Superpower (Platinum only) / Stealth Rock / Amnesia
-Super Fang / Curse (Platinum only) / Focus Punch / Toxic / Shadow Ball / Dig / Thunder / Thunderbolt
-Waterfall / Surf / Blizzard / Ice Beam
-Rock Climb / Strength / Hyper Fang
Explanation : Bibarel is just so versatile meaning it can fill most rolls a team needs. Need something for Crasher Wake ? Thunder, Bryon ? Dig, Fatima ? Dig, Thunder, Defense Curl + Rollout, Shadow Ball, (Diamond and Pearl only) Volkner ? Dig, Strength, Rock Climb, Thunder, Superpower, Return, not that you should use Bibarel against him but it can be useful in an emergency, Aaron ? Stealth Rock, Rollout, Strength, Rock Climb, Dig, Return, Surf, Waterfall, Blizzard, Ice Beam, Agatha ? See Aaron but take away the normal and rock moves, Flint ? See Aaron, Lucian ? Swagger, Amnesia, Strength, Waterfall, Rock Climb, Shadow Ball, Super Fang, Hyper Fang, Take Down. Each moveslot has different reasons for the moves in it. Slots 1 and 2 are utility, stuff you can throw on when you need it then take off afterwards, Slot 3 is for general ground-type killing, water moves for the Graveler and Steelix endgame, ice moves for the victory road dragons, Slot 4 is just for rounding it out with a reliable STAB, Strength can't miss if there is no accuracy or evasion modifiers, Rock Climb is the most powerful, and Hyper Fang can form paraflinch when combined with thunder wave.
Pros : Can be tailored for most things, can sweep Flint after Sunnybeam users go down in platinum, can wreck the victory road blissey with Yawn or Super Fang, comes early and can have a good moveset by Fantina in Diamond and Pearl, gets an 80 Base Power STAB move before most things are ready for it.
Cons : Weak without setup, Simple causes Superpower to drop attack and defense by 2 stages.