Not much since I keep a good set of stuff in my laptop bag.

I did keep a flashlight there for a while, but the company finally bought some after a fire scare in a dark server room during a power outage. I wasn't there for that, but nobody else thought to check my desk for a flashlight. Heck, nobody could even find the fire extinguishers for a while. (Hint: they are next to the stairwells.)

I do keep some extra food and water in my desk. I should keep more water, especially since we stopped supplying bottled water to employees. But I usually have case of bottles in the car.

Other than that, it's mostly junk. A screwdriver assortment, a junk knife, some expired cold meds, etc.