Most common dips:
Barbarian: 2 levels-fast movement, uncanny dodge and rage
Fighter: 2 levels for feats or 4 levels for weapon specialization and melee weapon mastery
Monk: 2 levels for Unarmed strike, evasion, +3 to all saves, Combat Reflexes, and Improved Grapple.
Rogue: 1, 2 or 4 levels...