Every year at SHS we have the "Senior Assassination," in which all participating seniors are given a target to be "killed" with a watergun. When you kill someone, you get their target. If you are sprayed by your target in defense, you are out for 24 hours.
Not content with the power of traditional super soakers, I intend to build one.
History of super soakers (click for fullsize)
I can see three supersoakers which I have owned on this chart, which is pretty cool and somewhat irrelevant. (All from the 2k series, BTW)

The Weapon:
Anyways, this page has a list of tutorials for building a homebrew supersoaker.
The APH
Models range from the fairly simple (yet powerful) APH, which has a range of 55 feet and surpasses all retail guns in range, output, and water capacity:



The SupercannonII
...To the SupercannonII, with a maximum range of 70 ft:





I'll probably make the APH; it has the most output (50 oz/sec) and has more than enough range. Plus it's the simplest to make.