what kind of spider is this?

[UnklSnappy]

The kind that lay their eggs in your ears while you sleep.
You better buy a WaxVac before they hatch and burrow into your brain.

 

[GobBluth]

Nuke it from orbit!!

 

[destrekor]

After looking further, I think it is a male cobweb spider..

The markings are on the top side of the spider...widows have their markings on the bottom side...

http://en.wikipedia.org/wiki/Triangulate_cobweb_spider

If it's anything other than a widow species, it's almost certainly a cobweb spider. I can't believe I forgot to think of that - many cobweb spiders can closely resemble widows, and they can often behave in a similar fashion.
Which makes sense, considering widows ARE cobweb spiders (all cobweb spiders share the same Family, of which the widow Genus is within).

But don't confuse the specific marking situation as a way to absolutely rule out it being any variety of Widow. Some widows, even of the exact same species, sometimes have a very different marking, different color, or none at all, or on the top of the abdomen. That can be especially true when they are young, with the markings possibly shifting to the underside as they age.
Plus, there are definitely widow species with varied markings on the top of the abdomen - it may just not be specifically the black widow.

I think I found it:

Neoscona oaxacensis - Western Spotted Orbweaver

I can all but guarantee that is not an orb weaver.

 

[Lemon law]

I am not a spider expert, but long odds, if we are talking the Dallas region, its harmless. If you leave it alone it will leave you alone.

 

[fralexandr]

could be a triangulate cobweb spider as previously indicated. The following picture seems to have a more similar pattern to yours, but this one might be female due to the larger abdomen.
http://www.biosurvey.ou.edu/okwild/misc/tricob.html
a good description for the triangulate cobweb spider
http://lancaster.unl.edu/pest/resources/triangulatespider.shtml

might also be Steatoda grossa
interestingly that's the spider used in the 2002 spiderman?
http://en.wikipedia.org/wiki/Steatoda_grossa

might be a noble false widow, but they aren't known to be in texas yet. the pattern is almost exactly like that, though I don't see any hints of a white band in your picture, it might just be the angle.
http://bugguide.net/node/view/716611/bgpage
http://en.wikipedia.org/wiki/Steatoda_nobilis

Doesn't look like the western spotted orbweaver (body shape and lack of large spines on legs) and isn't a brown widow.

I agree with destrekor on it being a cobweb/widow, seems highly likely it's a spider in the genus Steatoda though it might not be the one you linked
http://flickrhivemind.net/Tags/steatoda/Interesting