I was playing The Elder Scrolls IV: Oblivion and I was walking outside of the Imperial City when a guards head popped out of the water. "STOP! YOU HAVE VIOLATED THE LAW"

I was then arrested by a floating guard head.

Well... a lot of weird stuff happens in the Elder Scrolls and such, but I think the weirdest thing that happened for me was when I played Ridge Racer (don't remember which one though...)

I was playing normally when suddenly, my car floated in mid-air, spammed randomly by turning very fast and going everywhere on the map... and then, I past the finished line. It was probably a bug, but it only happened once.

Still, I re-did the race after (so I would feel I won with my skills, not with a bug), and the bug didn't happen again.

Once while playing TF2 a Demoman killed me than died immediately afterwards, so the deathcam was a floating bloody head that stared right at me and into my soul.
I defecated my digital pantaloons.

Oh, wait, I remember an other moment: it happened when I played "Battlefront 2". Sometimes, when you died by falling from a platform in some maps when playing online, if there were no players to look at (like in CoD if you die), the camera would follow your player falling thru the map, revealing squares of all kind.

I remember that I once I was playing Fallout: New Vegas, I put a live dynamite into somebody's "pants," and I remember how it didn't explode. I was wondering what was happening, and then I noticed something. They started to attack me, like usual, but by without moving anything at all. I questioned it, then after I killed it, I walked towards some area. I was randomly taking damage, here and there, I didn't mind it too much, but then something happened. I heard a bang, and my character went flying into the air. After my character hit the ground, it went back in, and continued that process. I was questioning what was happening, but then I reloaded my save, tried it again, and it didn't work.

I was playing FNV and I was at the NCR tent at Prim to start a quest. So I talk to the guy for the quest and skipping through the dialogue just to hurry it up and I turn around and I see Victor glitching under the tent exit, smiling at me, and spinning in circles. It creeped me the hell out of me.

I once played Killer 7. That game itself was the weirdest thing that happened to me. Such an odd game.

So I was playing Fallout 3 and was going to do the Super Market (or whatever that place was called) mission. When I walked in there I immediatly saw a thug, so I shot him without VAT and got a headshot so his head exploded. Then his body flew up to the sky, and when it fell down it started to bounce around in the market. It looked silly as hell and didn't stop until I left the building.

Once Skyrim playing, I was killing some giants out Whiterun, Lydia inadvertently hit one of Khajit, this guy followed me into my house, and when I killed him, he came back from the dead, again went to do a quest to get a daedric relic, which had to take a follower to an altar and kill him, I was in the Companions, it happens that I would ask one of them to follow me but he was always asking the same thing, although I accept he followed me wherever I were in dungeons and even Sovngarde. It was very annoying, just killing him.

Another when I was married, all my old followers appeared and that even dead companion followed me and kept asking myself the same thing.

It was horrible.

One time my brother and I were playing Banjo Kazooie multiplayer. I pressed the start button to pause the game but instead of it pausing, my brother's character exploded and I got points for it. It was awesome.

There was another time I was playing the CoD: Black Ops campaign on PS3 and I was in the level where you're in the lab towards the end of the game and for some reason, all the NPCs were floating with their arms sticking out and not moving. I made a video of it when it happened. All the guards floating were ones that I had killed already when you first go through that lab earlier in the game.

Middle of the night, hittin the old Super Nintendo for some good nostalgia, playing Super Metroid... When suddenly, A CAT. NUUUUUUUUUUUUUUUUUEEEEEEEEEEEEEEEEEEEEEEER, he flys like a lightning bolt into my SNES, I was fighting Kraid ( I think thats his name) and it glitches, that roar that he does every now and then, turned into what sounded like a scream with the now glitched SNES. Did I mention it was in the middle of the night? Well it was, I kicked the game out of the socket and ran out of the room. I lost a very important save that day as well.

Playing Fallout 3 and my ccreen goes multi-color with triangles scattered around. I could move and interact but couldn't see what's going on.

I completed a Hitman 2 mission using the same outfit and with a gun
killed the target and got away.Winned the best rank of the game.

This was one of the weirdest moments I've ever lived. F*** that game.

Haha, I love how most of these odd things are from Betheda games.

Well, one time in Mass Effect, I was exploiting a bug to get money, you had to go up and down two floors to do it. Everytime I did it, a Turian in the corner would be lifted up off the ground slightly, I did this for a while, and before I knew it he was up in the ceiling.