D&D 3.5 gestalt and monster races
And, incidentally, don't give all the monster powers at level 1. Build up towards them as you gain levels.
The Ogre Mage has a lot of benefits, so let's see what we can do with it...
Level 1: +2 Strength, Darkvision, Darkness 1/day, Disguise Self 3/day. A sorcerer with limited spells.
Level 2: +2 Charisma, 40' move, Charm Person 1/day. Mobility and charm.
Level 3: +2 Constitution, +1 Natural Armor, Sleep 1/day, Levitation (self only) 3/day. Tougher, starting to take off.
Level 4: +4 Strength (total), +2 Intelligence, Spell Resistance 7 + Level, Darkness 3/day, Invisibility 1/day. Sneaky and hard to affect.
Level 5: +2 Wisdom, +2 Natural Armor (total), Fly 3/day (speed 40', self only, replaces Levitate), Alter Self 3/day (Small or Medium humanoid or giant only). A lot of iconic abilities come on line.
Level 6: +4 Charisma (total), Large Size (no further attribute modifiers), Fast heal 1. Not much magic power, but builds on the base.
Level 7: +4 Constitution (total), +3 Natural Armor (total), Gaseous Form 1/day, Darkness at will. Tough and hard to catch.
Level 8: +6 Strength (total), +4 Intelligence (total), Flight speed (replaces Fly), Fast Heal 3, Alter Self can be used for Large sizes, Invisibility 3/day. Power and a little inherent magic.
Level 9: +4 Wisdom (total), +4 Natural Armor (total), Cone of Cold 1/day. Overall improvement.
Level 10: +8 Strength (total), Fast Heal 5, Invisibility at will. Almost completely done.
Level 11: +6 Charisma (total), +5 Natural Armor (total), Change Self (no longer has Alter Self). Polishing off the last bits.
Level 12: +10 Strength (total), + Constitution (total), Regeneration 5 (replaces Fast Heal). And done!
I tried to spread the powers across levels where they're be appropriate, and stagger them so they'd increase over time. Other approaches are possible as well, of course - the last levels are a bit lackluster when compared to what a normal class would be getting (but delaying the early bonuses might not help much).