The worst I think I ever did was ...
I was at a fast food restaurant and I ordered my meal without tomatoes. At the time I was having a bad allergic reaction and I suspected tomatoes as the culprit.
When my item came I checked and, sure enough there were tomatoes on it. I asked them to remake the order but the clerk replied, "Well, just take the tomatoes off. That's what we do." I was livid. When you have a food allergy you can't just remove the offending food once it has contaminated everything else.
I ended up removing the tomato slices and slapping them down on the counter. I left the meal item there, too. Then I stormed out. Trust me, I felt like throwing something but I didn't.
Okay, now that I've thought about it, I guess when I get mad I have much worse (better?) ways of getting my point across without throwing things. People who have seen me angry - really angry (and it doesn't happen a lot) know not to be in the path of my wrath. And I don't even yell. Actually my voice gets really quiet. I once worked at a really stressful job and a co-worker who unfortunately had seen me get angry ONCE nicknamed me The Raptor. The person who witnessed my anger (not AT a co-worker, thank goodness) said I could rip their head off, hand it back to them and do it in such a way THEY would thank me for not doing worse.