Wands make me thinking about generic fantasy. Wands are probably the easiest to devise because they can be a bit similar to present devices. Even so, other items can malfunction in sensible, but
another, less-modern way.
It should be quite simple with weapons, but it would require detailed, complex fighting system.
For example - swords (or other blades - making assumptions as '[rather] long, double-edged cutting weapon').
Parts of sword are: pommel, grip, cross-guard, fuller, edge, central ridge and point (I take names from
this, I don't know english words for these parts).
Pommel: improves balance; if damaged: - to-hit
Grip: gives a firm, hmm, grip; if damaged: - to-hit, weapon can fly out of hand
Cross-guard: gives protection; if damaged: - defensive value / evade / + to-hit for enemy
Fuller: imparts sort of flexibility... but I cannot imagine, how this can be damaged... but is possible to make blades with and without fuller; these with fuller will be more resistant to breaking in half
Edge: to cut; if damaged: - damage, - armor penetration
Central ridge irrevalent in this context
Point: ability to 'sting'; if damaged (for example - point can be broken off): ability not available
I know that this isn't exacly what you have in mind, but... it fits
and I don't know how so simple items can malfunction in another way.