What kind of night sights do you all use?
I like the look of the Trijicon night sights, but I've heard that they will get ruined if you get oil or cleaner on them when you clean your gun.
Funny that no one mentioned lasers...
First accessory for me would probably be one of the LX2 LumaMax dual output LED handheld flashlights that KeithD mentioned. Seems like it would be helpful in self defense mode and a good tactical flashlight with the two stage button on the end of the light.