They do 15 points of base damage (not sure how much it is for other races, but it feels much lower when I'm in a fistfight), but there's a heavy armor perk that has your gloves do their armor rating in damage (e.g., 25 armor = 25 unarmed damage), and there's a guy in the Ratway in Riften who has the Gloves of the Pugilist, which adds 10 damage to unarmed attacks. With enchanting, you can destroy the gloves to learn the enchantment, which can then be placed on any gloves. So, thanks to all that, my Khajiit (who is only in steel armor at this point) is doing more damage with his bare hands than any of the heavily armed enemies he's run into so far. He'll never have to use any weapons, except for the occasional arrow to get a high-flying dragon's attention.