I tend to block out my most serious bonehead moments, but I did once get so into playing a computer game that I forgot about a REAL tabletop game I was supposed to be playing in. Fortunately the GM got bogged down at work and canceled the game.
My only car accident involved me turning left into the back end of another car for no apparent reason. We were both going slow so there was no real damage, but it was still really stupid.
My employer once sent me out for a training seminar. I went to their website for driving directions and clicked on the "Dayton Center" directions. Well, unbeknownst to me this was a general link to their "directions" page instead of a direct link to only the Dayton Center directions. So I copied down the first *set* of directions without thinking and proceeded to drive to Cincinnati through rush-hour traffic and construction, find out I was in the wrong place, and have to drive all the way back to the other training center. Two intersections away some lady rear-ends me at a stoplight. This was the day my grandmother died. Needless to say, I was Upset.
When my family went to Hawaii for vacation I misread the date on my return flight and wound up stranded at the airport 24 hours earlier with little money and no rental car. The Ramada Inn gave me a Distressed Traveler discount for a room. I was a little surprised that they'd give those out for being a dumbass.