Stuff People Make Facebook Profiles For.
#1 - Cats, Dogs and other pets.
I've had a fair few friend requests from cats and dogs. Usually this bores me, however, now and again I have found myself thinking 'yeah, that dog is pretty funny, he deserves his own Facebook'. Of course, cute animals seem to be the second most popular thing on the internet after that thing they are trying to ban so it isn't that surprising.
#2 - Stuffed toys.
Also had a fair few friend requests from these. It usually seems to be a bit of a spur of the moment thing. They think it's a good idea, upload a few status updates from the perspective of the stuffed toy and then never touch it again. One of those Facebook friends you immediately delete when you're having a Facebook clear out.
#3 - Toddlers/babies.
At least making a profile for a pet or a toy is harmless. To me, there is something inherently odd about making a Facebook profile for a toddler. I had one contact who tried to send me a friend request from a profile they had made for their three year old. This profile had pictures, personal information and nonsensical writing supposedly bashed into the keyboard by the child that would say stuff like dhfuriodsfbjnvbSDJH. I didn't get it either.