Eladrin Paladin
Teleporting to aid an ally is always good. Plus you get a bonus skill, which is always useful.
Eladrin Cleric
Again, the fey step is always useful, along with the extra skill.
Tiefling Fighter
The bonus to hit bloodied opponents is useful, and you will often be able to make use of that other tiefling ability (I forget what it's called... the one where you smite someone who hit you)
Dwarf Rogue
Low-light vision is great. Dwarven durability is great for any class, but think about it for a rogue: your there in combat, stabbity stabbity, and the bad guy clobbers you for a bunch of damage, you can get your second wind (healing AND +2 to defenses) without wasting your attack, giving you a chance to murderize your enemy.
Elf Warlock
You are very mobile with your extra square of movement as an elf, and can maneuver over bad terrain without problems, both are great for a skirmisher (I'd advise fey pact for this, mechanically and thematically); you can also easily qualify for the ranger multiclass, which is awesome for a warlock (grab the stealth skill and hunter's quarry 1/encounter).