Most of the "weird stuff" was in my teens, or earlier. My dad caught me humping a stuffed animal one time, it was a raccoon. I have vivid memories of excess friction and stuffed animal hair stuck to my little dick, not sure if this is fucking though because there was no penetration.
For fucking, I would have to side with
@1lostnate, I attempted to fuck the crack of the couch on several occasions...I'm talking 10 to 12 years old, no grown adult should be doing this, there are way better things out there to penetrate, or be penetrated by...
Oh yeah, I did do the "microwaved wet sock" thing onetime, I must have been really horny, it felt ok I guess.