here are some of my other favorite scenes i've seen recently on Gags:

they have a pretty young girl dress up like a trashy street girl and ask passerbys for a light. when they pull out their lighter, she suddenly shoves a stick of dynamite in their face. a lot of them freak out and just walk away. but some of them actually light it for her - and after they do she gets all scared and drops it and runs away. then the person who lit it does the same thing.

and one of my all-time favorites:

as citizens are taking drinks from a public water fountain in a park, a construction worker comes by and nails a big sign into the ground near the fountain. just as they stand up again, they see the sign. on the sign it has a fountain symbol with the big red circle with a line crossed over it. and just under that is a big huge skull poison symbol. so the citizen starts thinking that he or she was just drinking poison. the reactions on their faces were truly classic.