What is this thorny tree?

[WDH]

Those other thorny things scratch.  Ty's specimen scars  .

[Texas Ranger]

OK, hercules club

[tyb525]

And they take over in the blink of an eye! My grandfather had one stick in his head when he was mowing underneath one. I've had countless holes and scratches in my body from them, and my dad has had them poke through coveralls and jeans into his leg, sometimes breaking off under the skin requiring home surgery to remove.

[Paul_H]

"Out west along the coast mountains the understory in places has a nastier shrub called the devil's club."

Oh Yeah!?!?  Well down souther'n here the sandspurs are the size of golf balls.  They're a lot worse than your club thingy

sez you

[Tom]

Yep!  I've been in a thicket of both.  Sandspurs will stop you dead in your tracks.  

Looks like I was wrong in calling that a devil's walking stick.
http://www.lnps.org/articles/ToothacheHercules.html

[SwampDonkey]

Pretty nasty Tyb. The New Brunswick cold keeps all those thorny things in their rightful place. Well except hawthorns, you ain't walked a grown in pasture of Hawthorns yet. I had one guy ask me to cruise a lot with a grove of that stuff out front. Nope, not going in there.