Tried: Googling the actual ideas I had, leading to various Wikipedia and even TVTropes and Straight Dope articles. Stuck now because I've basically self-debunked everything I could think of and now I'm out of ideas. Checking "could x work" if I know what x is happens to be a lot easier than "what sort of things could work" if I don't.
Question: I'm looking for a maneuver a character could do on another character he suspects to be dead, to make sure he's dead. The idea is that it can be tricky to tell the difference between lingering comas or vegetative states or whatever and actual clean death when one is stuck out in the wilds with no medical access or anything. Furthermore, guessing wrong and burying someone who's only mostly-dead (or leaving them to the advancing enemy if we're talking casualties of a battle during a major retreat or something) would be a horrible way to go. Therefore, a certain character (who is ex-military, if the badass and combat pragmatist qualifications to pull this off were in question) believes in basically re-killing corpses just in case; if they were already dead, then it's not like desecrating the body any further really does anything, so whatever, but if they weren't, then it's a mercy kill.
The question is, what can he do to do this? Extreme, extreme preference for something quick and relatively bloodless that can be done barehanded by someone with average-at-best strength, but if that's just impossible, then... well, I'll see my options. Beggars can't be choosers and whatnot. I at least want to keep the gore to a minimum (mercy-killing scenes tend to be emotional enough already without the ludicrous gibs added in) and I also want to remind you that their lack of access to the only remaining "live" cities prevents them from having anything fancier than a knife.
My first idea was pure Hollywood-style neck snap, but some basic Googling proved that idea to be utter nonsense. Oh, well.
My second was deliberately over-applying a rear naked choke (that chokehold that can cause unconsciousness in seconds but you have to be careful because holding it too long causes brain damage or death.) The problem there is... well, this comes up twice, and both have their own situation-specific reasons it's a questionable thing to do. One case hasn't been breathing or had a pulse for several minutes already (which, I know, should be enough to confirm death without having to do anything further anyway, but I still want him to perform some sort of coup de grace just for dramatic and character-establishing reasons) and it's not like obstructing the arteries that give blood to the brain really does anything that wasn't already happening due to the lack of pulse. The second is a "crap, the enemy will be here shortly, I don't have time to actually bury this guy so I'm just going to finish him off real quick and then run" case, in which it seems like he wouldn't really have time for a several-minute chokehold, either.
My third idea was... um... to ask you guys, I guess. :(