There's a very common cactus here in the Southwest that I don't write about much because I don't like it, but now that it's blooming I thought I'd introduce you to what I consider the nastiest, most dangerous cactus:
The cholla
(pronounced choi-a)
The dead ones look like zombies (above) and the live ones are thick with barbed spines that are really hard to remove once lodged in the skin.
And they jump on you! If you barely brush up against one, it will break at a joint and attach itself to you, like what happened to these unlucky guys who I found by googling "pictures of cholla cacti stuck on people."
The first one fell while ATVing in the Nevada desert. I don't know what happened to the one below, but it looks like medical help has arrived.
In my four years of hiking here, I've never been stuck by a cholla because I'm terrified of them and give them a wide berth and a lot of respect. On my first Meetup hike here, our leader advised us to carry combs in our packs to remove cholla joints that might get stuck on us. There's no way you can remove them with your hands, because they would stick you again.