So for those who like Pen and Paper RPGs what're some crazy/awesome/utterly stupid things you've seen or done on a campaign?

here's mine:
so I've recently gotten into Pen and Paper RPGs. the group I'm with is specifically playing Warhammar 40K: Dark Heresy and I am the Adept class.

so on a campaign I was in recently we were investigating a cult for the Chaos god Khorne (I think that's how you spell it) we ended up getting into a battle with some cultists and our party psyker accidentally summoned a Blood-letter demon. (in Dark Heresy if you mess up badly enough casting a spell you can summon a demon from hell) This summoning caused mass hysteria and our entire party was put in a massive panic. We did not stand a chance, there were a few Sisters of Battle present as well, and even they were having a hard time.

Being the party adept the last place I need to be is in a full-frontal assault on a demon. (my class is specialized in knowledge and finding alternative solutions to problems) So trying to play my class right I decide to try and find something around the cultist's lair that might reverse the summoning. So I find a hidden passage way while the rest of the party is dealing with the demon and discover a little room within a cave that has a bunch of glyphs and a book of satanic incantations.
so what do I do?
I read the incantations out loud of course =D
that was one of the dumbest things I've done on a campaign. I rolled a 2 and summoned a nice little demon of my very own! I gained an insanity point for looking at it and my character went into a panicked fight-or-flight frenzy. I started running like mad further down the cave with the demon hot on my tail. It was pretty damn scary.

I always use to think the idea of a horror themed PnP RPGs was kind of silly, how can something like DnD or Dark Heresy be legitimately frightening? well I admit at that moment I felt the same way I did when I was being chased by a monster in Amnesia
"OH [censored] OH [censored] OH [censored] RUUUUUUN"
as if reading my mind another player actually started playing this song http://www.youtube.com/watch?v=TR3v_eT8aCA as background music.
I kept running down the cave like mad with the DM describing in vivid detail how panicked and beyond reason my character was. I ended up reaching a dead end with a large opening over a cliff. I turned around and did the last thing I could do.
ducked
I rolled a critical on that duck and was unbelievably lucky for doing so. The demon lunged for me as I ducked and flew right over me over the opening and the cliff.
that was insane, the last thing anyone would expect is an Adept to survive a demon encounter alone. That little stunt was really the first time I felt my character was in true danger. The DM is usually pretty merciful about a death (normally he'll incapacitate you for the rest of the session, but not kill your character outright) and only prescribes it when a party member does something extremely stupid, and what I did, was extremely stupid. He had every right to kill me, and was going to were it not for that critical.

so if you skipped the long story here's the question again, what're some great RPG stories you can share?