All good things must come to an end. Eventually, your co-workers will become immune to your flying toy antics, and you'll need to come up with some other way to irritate them. So here's the answer you've been looking for: the black helicopter.
This way, not only can you buzz them at will, but you can also prey on their paranoid tendencies at the same time--the best of all conspiratorial worlds. The "Black Ghost," as first seen on Coolest-Gadgets, has "full altitude and directional control," which is a good thing because it'll need it when the other cubicle dwellers come after it to retaliate.