im not a guy but ive been told by a few guys some of things they have once used. here are a few of the ones that stayed in my head....
-a rolled up sleeping bag
my best friend used to tightly roll a sleeping back and fuck the hole at the side... it wasnt his either and he never washed it, which was even funnier
-a bag of lube/jello
he said he somehow made a device that he stuck under his mattress and he would fuck the substance while it was tight in the mattress. haha
-a stuffed animal
my girlfriends brother actually stole her giant teddy bear, cut a hole in the crotch area and fucked it..... hahahaha
thats all i can recall. you guys have to get creative to make things seem/feel like pussy. we girls have it easy... phallic shapes are easy to find.....