You know what is fun? Making deals with your PCs.
In my current game, my friend, Jason, is playing a Dark Pact Warlock. He wanted to give his character a little extra damage. I said "Yes, BUT..."
As a Dungeon Master, the "Yes, BUT..." can be a powerful weapon. I gave my friend the extra damage he wanted, but I twisted it with something partially story and partially mechanical. With each damaging power he uses, he has a chance to fall into a blind murderous rage, attacking friend and enemy alike.
Don't be afraid to make deals with your players in the interest of fun. Bringing in this unnatural rage not only makes the story that much more interesting, but offers a goal and some motivation for the character. He is now trying to find a way to stop the rage from ever surfacing again. Do I smell a Minor Quest?