I'm sure we've all done stupid things in the game, so I've decided to start this topic so we can all share in our embarrasing moments of stupidity, loss of common sense, and lack of good luck.
Please let's not use this topic to argue points of canon, gaming, rules. Opinions on wether the GM was playing fair or not however are encouraged.

Me (dwarfStreetSam) and Buddy (human combat mage) have just survived encounter with 6 legged robotic tank (as seen in "Ghost in the Shell") and have come across it's technical manual/schematics, we are on our way to the meet. Unfortunately we had one chasing us. Since I already decided I have a bone to pick with these things, and being a "to the bone" Dwarf I decide to give my buddy time to get to the meet. So, recieving target numbers, and rolling out those successes all the way, I Reload my 6 cylinders, 3 of them to be precise (in the middle of riding a motorcycle at 50mph) with Lead Coated depleted uranium rounds (garung*ddamnteed to pierce any armor) Reach out and activate my magnitic cyberlimbsystem to catch a street sign, Bike flies out from under me, I come to a stop in the middle of the street eventually, stand up, draw dual pistols just in time to look that thing square in it's sensors and say to it "Gimme your best shot pal, I can take it." and proceed to fire upon it.
bullet #1 peirces armor
ignites fuel tank
dwarf toast.
Thankfully the GM was impressed enough with Dwarf allready and allowed a "Ressurection". and so Weredigo (pronounced intentionally as "Where'd He Go?" ) joined the ranks of my favorite characters.

JackFrost, Bald Elf
Me and buddy were chasing some merc who had stolen a "SoccerMom Minivan". First time we were ever quized on our speed. Apparantly we were in moderate traffic. Both me and buddy did the stupid thing "Uhm, I dunno..." GM rolled Percentile to see how fast we were going, Buddy, 25, good safe speed. Me 86, was able to dodge only one car before veering into oncoming traffic, I hit a Jackrabbit, deciding on the "safe" thing I declare "I'm hauling my front tire off the road and Onto the car".... Jack rabbits have an upward sloping front end, just like a ramp. In mid air I kick off the bike and land into a street Lamp. That's not the worst. The Bike, borrowed from a chummer, sails on to land in the mall, in Neiman Marcus, Plows through the Lingerie display, and winds up rearranging the "Perfume/Cologne" counter. Had to pick the bike up later in a Chem Suit and a bunch of hired muscle.

I freely admit I have done and said some stupid things. In the game, those two take the cake.

Oh, by the way, Try and post that which your characters have gone through, not what you have done to your players, I'd rather not have this turn into a boast fest.