get like hundreds of cheap plastic cup's fill each one with some kind of liquid, then use something so you can flip each over without spilling, almminum foil, wax paper, whatever you can think of... flip each cup over, slip out the foil, wax paper or whatever and the water will stay in the cup until he picks them up.
cover every flat surface of his room with them, maybe dont fill up the first like 10 that he will pick up, so he thinks its just a bunch of cups in his room, which isnt that bad, then he will flip one over thats full of liquid and get extra pissed.
and get a bunch of misc flat, hard items, clothes hangers work well, take off the bottom sheet to his bed, lay out all the clothes hangers cover them back up, make his bed look like he left it, and when he gets in, it will just be annoying and stupid as hell, which seems to piss people off more. but this is only really good when its done along with a bunch of other worse stuff. so when he thinks its all over, after he cleaned up all the spilled liquid, or other pranks you decide to do, he gets into bed releaved to get some sleep, and its filled with uncomfortable crap, you could fill it with tacks if you wanna be extra cool.
put stuff in his shoes.
oh and if you really wanna piss him off to the max..... get an airbag, from a car, i dont know where to get one, maybe just check out a junkyard or somethin. put it in a box, a square box like 2 or 3 ft by 2 or 3 ft will work good. fill the entire thing with flour, powder sugar, and dont forget to add some glitter. put it all on top of the airbag, if you dont totally fill the box, use cardboard to kinda keep the flour away from the sides and right in the blast zone of the airbag. either set it up so it looks like he got a package, and rig it so that when he opens it it blasts his face. or set it in his room, so that when he walks in, you set it off yourself and it will completely fill his room, or maybe hide it somewhat well so that you can set it off when he's sleeping, i dunno. you should be able to figure out how to rig it since your an electrical engineer or whatever...
we did it to a friend, put the box on his doorstep, angled it slightly towards the door, ran a wire between a crack from the airbag to a car batter, rang his door, he answered and just stared at the box for awhile since it was late at night, then it exploded, completely covered him in flour, got in his socks shoes, etc.. got in his nose and mouth, covered his porch, and covered the inside of the house within like a 50 foot radius, made it upstairs, in his kitchen, bathroom etc.... those things are powerfull as fuck... it send like 40 lbs of flour and random stuff flying.
