If you're going to go down, go down with style. Failing your final exam can actually be an amusing experience, depending on what you make of it. Here are some suggestions...
Bring a pillow. Fall asleep (or pretend to) until the last 15 minutes. Wake up, say "oh geez, better get cracking" and do some gibberish work. Turn it in a few minutes early.
Get a copy of the exam, run out screaming "Andre, Andre, I've got the secret documents!!"
If it is a math/science exam, answer in essay form. If it is long answer/essay form, answer with numbers and symbols. Be creative. Use the integral symbol.
Make paper airplanes out of the exam. Aim them at the instructor's left nostril.
Talk the entire way through the exam. Read questions aloud, debate your answers with yourself out loud. If asked to stop, yell out, "I'm SOOO sure you can hear me thinking." Then start talking about what a jerk the instructor is.
Walk in, get the exam, sit down. About five minutes into it, loudly say to the instructor, "I don't understand ANY of this. I've been to every lecture all semester long! What's the deal? And who the hell are you? Where's the regular guy?"
Bring a Game Boy (or Game Gear, etc...). Play with the volume at max level.
On the answer sheet (book, whatever) find a new, interesting way to refuse to answer every question. For example: I refuse to answer this question on the grounds that it conflicts with my religious beliefs. Be creative.
Run into the exam room looking about frantically. Breathe a sigh of relief. Go to the instructor, say "They've found me, I have to leave the country" and run off.
Fifteen minutes into the exam, stand up, rip up all the papers into very small pieces, throw them into the air and yell out "Merry Christmas." If you're really daring, ask for another copy of the exam. Say you lost the first one. Repeat this process every fifteen minutes.
Do the exam with crayons, paint, or fluorescent mar(less)