It can be a bug, glitch, or something that's just plain creepy. For example, I just got into the NCR correctional facility when huge dirt colored rectangles appered every time I moved. It looked like a texture problem, but it did a pretty good job of scaring the crap out of me while fighting the powder gangers

Old Lady Gibson falling out of the sky and attacking me at Helios One.
A Radscorpion corpse stretched about 50m vertically into the sky.
My characters hands kept growing longer every time I drew a new weapon. After a few times his fingers were about half the length of his arms. This one was actually pretty damn creepy cause I didn't notice it right away, just rotated the camera after a while and nearly had a panic attack.
Travelling to the Prospector's Den in the middle of the night, some Powder Ganger with a bugged out face stops comes from nowhere and goes "I got a present for you, hope you like dynamite!" or something. I swear his face was bugged, he had the widest, creepiest smile I've ever seen.

Metalhead bighorners rocking up up in the wasteland. :mohawk:

Raul falling out of the sky and telling me about his past at Helios One.

I've also fast traveled on top of a bark scorpion. Scared the crap out of me.
Old lady gibson also fell out of the sky, then asked me to buy her merchandise

I was dodging missiles at Nellis, and i saw a legion explorer spawning ifront of me, telling me that the legion drop-box has been filled, and when he ran away, The bommers started to shoot missiles at him :vaultboy: He did a good job, but his slave-making ass were blown all the way to Mojave outpost at the finish line :rolleyes:

The other day I was doing that lucky old sun and I basically finished the quest and was going to talk to fantastic and old lady Gibson was out by the reflectors getting attacked by her own dogs and mole rats and got killed

Yeah, I just put the power to Archimedes II, and I didn't know the initial laser would kill all of the NCR. Good thing they don't shoot me on sight yet

Seeing a brahmin running from one gate of the strip to the other.

Things, mostly Gibson's dogs, falling into Helios One and attack the NCR guards.
Have a Bighorner ram/headbutt me and then bounce back and ping into the air.
The Freesider who tries to access the Strip without paying, he ran to the door and just stood there and the Sercuritrons took a full minute to notice and kill him.
The Sercuritrons blasting some graffiti on a wall.

I was doing Ghost Town Gunfight and I underestimated my character so I took out my grenade rifle and everybody in the town died. I couldn't even find half the bodies but I learned to use my powers for good and then I restarted with a new character since that one was awful.

Where did you get a grenade rifle at the start

With the Couriers Stash DLC you start with a Mercenaries Grenade Rifle and 20 grenades for it.

Pretty much any post in the New Vegas forum

The time when Sarah Wientraub spawned in the Ultra-Luxe
The time when I was in the Hopeville Army Base area of the Divide by the missile you have to destroy to get near the high road cavern, a Marked Man was trying to find me (He was on the other side of the wall) and he magically warped on top of the nearby telephone pole, then the right in front of me. It was pretty weird. >_>

Was walking around freeside and noticed, when I switched to 3rd person, that whatever weapon I had equipped was only half its normal size. Looked like my character had a toy gun. Lol.

Shooting any animal/human with the Sturdy Caravan Shotgun in a new game at level 7 and they all run away and hide behind things, when i get near, they run away again... wth ??
same thing currently happens with the Legion (Vilified), the Centurion death squads come charging at me, the moment i fire only that weapon, they turn around and run away and hide.
currently playing at level 7, "very hard", "casual" with ed-d and boone, all dlc's installed on ps3 console.
surely, it has to be one strange glitched bug, ive never seen this happen, nevertheless, its fun lol.

Seeing a Brahmin run across The Strip and the classic dead body glitch is always a good laugh.

walking through freeside and vatsing a goon like usual but when i shot him he flew up un the air then i shot again and killed him