For me it was back in 1996, when I saw
sparks around my window after a extremely wild
thunderstorm. The power was out, and there was
no electrical wires or anything near the window.
The next day, I heard on the news that firefighters were getting shocked from their
truck, because of all of the static electricity
in the air.

The phenomenon has long been known, especially to sailors, who called the sparks "corposants," "St. Elmo's Fire," or named individual corpusants after Leda's children (Castor, Pollux, Helen).

Another article about it can be found here.

I heard of a guy who got mildly zapped through
the shopping carts he was pushing when lightning
hit a nearby light pole.

Being from Connecticut, living in Mississippi for the first time, noticing the lightning storms there. I was quite amazed at how the lightning would zip out and snake along underneath the clouds and go for some lenths before going out. Never saw anything like that in Conn.