Aside from those obvious moving-part failures like hard drives and cooling fans, I've had all sorts of things mysteriously fail:
several of those ADSL filters that plug in to the phone socket,
one of a pair of CPUs (not through overheating, it just died),
RAM in a desktop,
a PC power supply (not the fan - that was fine - the control circuitry went doolally),
USB drives (I suppose they suffer some mechanical stress),
and most weird a single port in a 16-way gigabit switch...
Solid-state is not necessarily forever.