I initially came on here to post about this sweet video I found on Newgrounds, but upon going to the site my eye was immediately lassoed by this: The Charlie Sheen Game. Cops try to murder you as you race through the streets, picking up hookers and murdering innocent bicyclists. It's awesome and definitely worth five to twenty minutes of solid action.
The video I first had in my mind is this awesome Harry Potter parody. It has two sequels, and it's about the endless struggle between the wizards of Hogwarts and the saiyans of Dragon Ball Z. Sounds nerdy, and it has a ton of references to things you won't understand without some history with these video games/cartoons/novels, but seriously, THE SUN WAS DESTROYED BY THE GRAVITY OF THEIR WEIGHT!