Lets see, Bloody fish guts on a buddies windshield. Needless to say he wasnt too thrilled about it.
Here is a good one to do to a buddy who always has his rig shuttled and has the keys put in the same place. Make sure you beat him to the take out. Grab his keys and move his rig up the road and out off sight. Then hang out at the ramp and watch him freak out about his truck being stolen I did this once, The look on my friends face was priceless.