Bad prop handling, in general, bugs me. Good prop handling makes me ridiculously happy when I notice it.

Two people typing on the same keyboard, or someone reading a computer screen while looking above it at the air, throwing their laptop around like laptops aren't delicate and don't cost real money... pretending to have a full cup but swinging it around so it's blatant there's nothing spillable inside... gunfights where a gun has no clip in... driving by swinging the wheel back and forth dramatically... that sort of thing.

Act like you're in the imaginary world you're supposed to be in!

Pete Postlethwaite, Dianne Wiest, and Robert Downey Jr are all great prop actors, even with green-screened-in-later digital props. Their characters know that food is for eating, coffee can spill, and computers have to be used, not just vaguely gestured with because hoodledeeepoo! magic.