What would be a fun way to quit your job?

Rent a limo. Have it pick you up at work around 10:00. When it shows up yell across the room to let the boss "I am outta here". Wave goodbye and don't look back.
Go outside, get in your limo, and head towards the state capital to claim your lottery winnings.

Shit on your bosses desk

Piss in your bosses chair. Set the place on fire. (Semi-kidding)

Key your bosses car. Misfile everything that day so they can figure it out tomorrow. Shred or erase important documents. Sign their phone number for various sex sites. Imply things to main branch office that will lead to an unnecessary and costly internal office. Poor soda on equipment. Download viruses onto their computers. Change the opening webpage to a sex site. Call their clients and tell them they lost their stuff and be an a-hole about it. Jam gum in all the locks. Set off the fire alarm. I could keep going but you get the point. Be creative.

1: glue all the office supplyies to the roof
2: freeze some "gelled shaving cream" cut off the can, leave the chunk to thaw and expand in the bosses desk
3: if they allow fish tanks in the lobby or office/desk/ anywear will work: fill the tank with cheap beer, put canned anchovies into it...the icing on the cake is to talk to them, feed em, ect...
4: just show up and sit at your desk...termination process is not usually so instant...and just sit there all day. this works for all jobs except security. just zone out and get nothing done...
5: pick a really lame joke(yo mama so fat when see sits on an airplane she sits next to EVERYBODY) and repeat that to every costomer/employee/person you see all day repeatadly!!!

For all you Office Space fans :

"No, it's not ok because if they make me...if they take my stapler...I'll have to set the building on fire."

or

"It doesn't matter, I don't like my job, and I dont think I'm gonna go any more.
- So, won't you get fired?
I dunno, but I really dont' like it, so I'm not gonna go any more.
- So you're gonna quit?
No, I'm just gonna stop going. "

Well, at my last job, when anyone was laid off or quit, they'd watch you clean out your stuff and then escort you to the door and take your keycard. The guy who always did it was a really unpleasant person (I won't say exactly what I thought of him, I might get banned), and if I'd gotten laid off (I did, but it was when the whole company went under, and he'd been laid off before me), I was going to say to him 'John, can you walk me to my car too?' Knowing him and his false sympathy, he'd say sure. Then I'd grin, and say oh good, can you stand still while I run you over on my way out?...

Alas, he got fired before I was laid off, would have loved to see the look on his face though.