Of course, all pie provides enjoyment. But to be called "fun" requires a little something extra. Pizzazz.
There's always the basics - making a face or fun shapes on the top of your pie, etc. But you can do better. Submit your creative pie ideas!
The origins of this picture are unknown (please speak up if you know to whom the
credit should be given), but it speaks to the math nerd within. 
Behold, the Area
Pie:
The Pie Maven does not condone vandalism, but if you must vandal, this is the way to do it:
HOW TO HAVE A SUCCESSFUL PIE FIGHT:
1: Use lightweight, flimsy pie pans. (This is the only time the Pie Maven will recommend those useless things.)
2. Buy the cheapest pre-made pie crusts you can find.
3. Fill the pies with just whipped cream, or a light pudding cream.
4. Whipped cream from a can works best because it's airier.
5. This cannot be emphasized enough: have the fight in a place you can easily hose down. Unless you don't care about it stinking later.
6. Similarly, wear clothes you don't mind getting gross.
7. For extra fun, build a warzone, with bunkers and cover. If you fight out in the open, the fight will be over in seconds.
8. Do NOT use any pies that contain raw egg. You don't want anyone getting sick. (It's rare, but there have been salmonella cases caused by raw egg in the ear. Strange, but true.)
JOKES:
(The Pie Maven is not responsible for the creation of these jokes and makes no representation as to their level of humor or taste, or lack thereof.)
One day Mary, a mom of 3, was making a pie for her kids. Johnny was 5, Steve was 10, and Michael was 15. Steve had a BB gun and left the box of BBs on on the kitchen table. While Mary was cooking the pie she turned and the box of BBs fell into the pie mix. She decided not to worry about it and left them in without telling her children. After dinner, the dessert was the pie and every kid had 2 pieces. The next day when they got home Johnny told his mom that he peed out little silver balls and Mary told him not to worry about it. Then Steve came to her and said the same thing and she told him not to worry about it. Then Michael came to Mary and Mary said, "Let me guess, you peed out little silver balls." And Michael said, "No I was jerking off in the kitchen and I think I killed the dog!"
What's a competition that never ends? --A bulimic pie-eating contest
What's good on pie but not on pussy? --Crust
What's the difference between a dead baby and apple pie? --Chuck Norris doesn't eat the apple pie after he has sex with it.
The geniuses at Evil Mad Scientist Laboratories created this awesomely fun Apple apple pie using a square springform pan (and even went impressively übergeek and used a 45 watt carbon-dioxide laser for the lattice):