I have a few times and am not even remotely proud of it. Actually, more than a few times.

This last summer I had a two day period where I was harassed by motorists several times while riding perfectly legal. The first one I handled nicely with only a WTF gesture while I was riding after the motorist cut me off and honked at me. He then pulled over to challenge me to a fight. I went on my merry way.
The next day some genius honked at me while we both were rounding a narrow turn and I completely lost it. Many a f word, middle finger, and me telling him to pull over so we could discuss it. He took off.
I spoke with a few friends and they thought it was due to the long hot summer and that had everyone on edge.