Dress up as the grim reaper and lean agesnt a poll and just watch the traffic go by
Get a camera and start recording people driveing by wearing a BIG sign saying 'I SEE YOU'
Grab a bunch of you crazy friends dress up in halloween costumes and wave and laugh and make calls out to the cars stopping
(if ur a guy) wear a big trenchcoat and under it wear a ballerina outfit and flash people
(if ur a girl) wear a big trenchcoat and under it have a tight tight bodysuit and stuff ur pants like a guy and stuff one boob extra big and flash people
Park your car on the side of the road and point hairdryers at passing cars. If you have no car still just point hairdryers at cars and watch them slow down.