A couple of years back I was in a fairly large and successful World of Warcraft guild. One night, while raiding one of the easier instances--Molten Core I think--one of my guildmates began playing clips from an Arnold Schwarzenegger soundboard.
If you don't know what a soundboard is, it's simply a Web-based collection of short sound clips that are usually taken from popular--or better yet, not so popular--movies.
During the raid, whenever someone complained about something dumb, they'd get a quick "Stop whining!" or just a random "Put that cookie down"--usually enough to send me into hysterics. It probably doesn't sound like much, but I laugh at pretty much anything.
What I love most about this is that the sounds are clean versions of the audio clips, separated from surrounding music or sound effects. As an added bonus, the clips are mixed well enough not to cause my ears to bleed when listening through earbuds, unlike other soundboards.
Also, you can string together a number of clips and post them on Facebook or e-mail them to friends as messages. I just sent a real mushy one to my fiancee. Lets hope the wedding is still on.
Right now there are a few clips for most of the main rebels (Han, Luke, Leia), but none yet for the Empire. StarWars.com promises new updates every Friday all summer long. So hopefully soon I'll be able to string together some awesome Darth Vader clips.
If you're a Star Wars fan or just need to waste some time, I recommend checking it out.