First, no place to vote. But if there were, I'd vote for Jon. And he really needs to hang. Imagine that nice, long hair going every which way as he twists and turns on the noose.
Dave looks to be a swimmer. So let's see how good he is at holding his breath. Tie him hand and foot, put him in a bathtub full of water, and hold his head under till he drowns.
Brent looks like a cocky SOB. Slip something into the drink he's holding. While he's under, bind him. When he wakes up, open up that belly, and live gut him.
Jon is begging to be hung. Sneak up behind him with chloroform. Tie him, and when he wakes, first explore that treasure trail and where it leads. After that fun, strip him, noose him, release his restraints. Do a short or no drop hanging and let him show you his new dance moves as he chokes to death.
As for Keith, after overpowering him, and shutting up that girlfriend, I'd tie them both in the canoe, and send it careening over Niagara Falls. Of course, they'd both be naked.
Nathaniel does nothing for me, but if I were to plan his demise, I'd impale him live on a spit, put that green apple in his mouth, like the pig he is, and do a slow live roasting over a hot fire.
brent, hands down. id take a page out of the old west -- stake him out naked and spreadeagle in the hot sun, then tie a thick piece of wet rawhide around his neck. id tie another one tight around his balls. as the rawhide dries, it shrinks, slowly strangling him to death while the other cord squeezing his balls makes his last moments full of unbearable agony. while im waiting for that to happen, id rape his mouth over and over, torture his feet, and abuse that hot hairy chest every way i can think of.