1. Point to yourself and say "You could've had this!"
2. Work in a glitter bomb if you can, tastefully.
3. Set up a stuffed animal at your computer and see how long it takes before someone notices you're gone.
4. Wait until a quiet moment, then pop a balloon and say "I'm out."
5. Send a mass email to everyone on staff informing them that you're trapped inside your computer until a vindictive wizard decides otherwise.
6. Crouch down on the floor and crawl away, army-style, until you're out of the building.
7. Sneak up behind your boss and whisper "I'll never forget you."
8. Drop a ton of money at a magic store and puff-of-smoke on outta there.
9. Loudly play Semisonic's 1998 classic "Closing Time" while slowly backing away from everyone without saying a word.
10. Try to get everyone to form a midday conga line. If people refuse to participate, that's when you say "I've had it with your attitudes!" and hand in your two weeks notice. (In the unlikely event that you get the conga line going, lead it out of the office and then simply run away.)
11. Make 24 cupcakes. Use four of them to spell out "Nope." And then you can eat the other 20.