Hands down, April Fool's Day is an IT worker's favorite "holiday" because there are so many ways to mess with an unsuspecting computer user. Halloween runs a close second, though, because its the one day out of the year when we can fly our geek flag with pride. For instance:
Star Wars costumes -- Even though some of us still dress up in our finest Star Wars regalia on other days during the year, Halloween is when we can really let our hair down and roam the streets as a Ahsoka Tano or a Rebel pilot without anyone batting an eye. Don't forget your dog, too.
Scary surfing -- Even if you haven't been able to convince your CIO that open source is the way to go, you've at least convinced him to let you install Firefox as the company-wide default browser, right? Have everyone use one of these spooky browser themes for the day.
High-tech pumpkin carving -- Leave it to a geek with high-tech tools to take pumpkin carving to the next level. Speaking of pumpkins, one of the best kept secrets in IT is just how great the tech worker's sense of humor is. Well, the cat's out of the bag.
Evil Entity Linux -- Even the penguin spends Halloween on the dark side.
If these ideas are a little too over-the-top for you, how about just wearing a Pumpkin Pi t-shirt?