What in the hell is that thing? It's huge, I mean, it's bigger than a man, and it killed me in two hits. It's like a grayish color, gigantic, runs really fast, it was next to the area with the alcohol you can take and the bed you can sleep in (the shed area). And like right outside there. I was like "what the hell is that thing", so I armed my baseball bat and......yeah...it shredded it me. I have wild wasteland on, is that one of those crazy things that show up? I ran back to the same area, slept for three hours, and it's still here. Right now in front of me, but I don't think it's seen me yet. It's a 'Deathclaw' or something, I can't quite make out the name.

Probably a Legendary Deathclaw (or something like that) based on the pre-game information and your description. Just sneak around it, you probably won't be able to kill it at your level.

Possibly (cos i havent played NV yet) a gecko?

That's a Deathclaw...not to be messed around with until later, preferably armed with a very heavy weapon.