You know what really pisses me off when I'm at work (or anywhere else, for that matter)?
When people are in my goddamn way.
I don't know what it is about people being in my way, but there's almost nothing more irritating when it comes to human behavior.
I say "excuse me, sir/ma'am".
They just stand there.
I change my approach. "I'm just gonna slip past you for a sec."
They sort of move their cart/basket/gigantic ass a little bit. Usually in the wrong direction.
I end up testing the limits of agility just to get around them, then end up apologizing because I feel rude for having almost invaded their space despite the fact that they're too goddamn stupid to mind themselves.