Here's one I bet you never hear of.
Differential flaps in a C-310, flap cable for the right side snapped, makes for a very interesting adverse yaw situation. At first I thought I had lost an engine, the right wing dropped and I had a yaw feel, but then I realized things were bass-ackwards.
Other than that, flat tire on/during landing(student riding brakes!), transponder and DG failures, some other small crap I forget about.