Old school t.v. Gave it a whack on the side every now and again to keep it in order. Flat screen t.v's don't have the same satisfying width for rigorous smacking.
Yep I used to have a tv that required regular whacks.
Not really fixed but the hood of a friend's car was stuck shut once. On the tv show Happy Days the Fonz once opened a hood by banging on it so I said "Here I am going to pull a Fonzie move" and boom, it popped right open. I'm sure it was much funnier then as we were pretty fried.
Not that I can think of but I just wanted to say that my son refers to that as "percussive maintenance".
Um my computer!
Occasionally I heard a strange electronic noise. After a while I decided it must be my computer so I whacked it (gently). The noise stopped. Later I discovered it was the hard drive I had sitting on top of the computer. Luckily they both survived and have been quite since.
My humidifier. It makes this awful grinding noise whenever I turn it on, until I give it a good thump.
Old NES games, more times than I can count.