Celebii and Jirachi can do everything! They have 100 base of every stat.
Celebii can baton pass SD, Calm Mind, Substitites, etc. It can Sub Seed. It can run a Specs set. It can wall, it can status stuff, and it has natural cure (very good ability)
Jirachi isnt as versatile as Celebii, but it can tank, set up screens, wish pass, and attempt a sweep with Charge Beam and stuff.
However:
Salamence is the most versatile pokemon of all time. With decent defenses, intimidate, and over 350 of both offensive stats, SalaMENACE can destroy things if you mispredict it's set. It's offensive movepool includes Dragon Claw/Pulse/Meteor, Flamethrower/Blast, Hydropump, Earthquake, Stone Edge, Rock Slide, Brick Break, Aerial Ace, Thunder Fang, Fire Fang, you name it, it has it. It gets DD (the best stat-upper) by breeding. Also, Salamence can Wish pass is you have the NYPC version.