Homunculus

Homonculi can be found in Karazhan. They provide 3 reputation with the Violet Eye when killed.

Kirin Tor doctrine frowns upon making homunculi, but some understand the principles involved.

Attacks and abilities

 * Fire Bolt: Strikes a single target for 700 fire damage, fast casting.

Strategy
These come with Shadow Pillagers and there are frequently several of them. Have your warlock use Enslave Demon one of them and Banish another, they're pretty easy to burn down.

Besides a decent attack, the large mana pool for these demons is ideal for the use of Dark Pact.