1. A person at the absolute top level of uniqueness and awesomeness.
2. A person who displays consistent badass and insane behavior, much like those on the TV show, Jackass.
"Who went with you to the concert?"
"Oh, a couple of my friends, and there was this one Halstead guy that nobody knew, but he was pretty awesome."
"Think light yourself on fire and laugh."
"Whoa....That's pretty awesome."
In poker, playing a "Halstead" refers to playing a Jack Deuce. Often successful at taking the pot with this hand, there are few that like getting beaten by this combo.
I had a halstead and he went all in, I flopped a Jack and caught a deuce on the river giving me two pairs to his one!