Some preliminary conclusions:

- "A and B [...] work a lot better individually." So they probably separated while collecting firewood.

- "A has OCD and can't stand things being messy. [...] There's a pile of firewood at the campsite, piled extremely neatly." So the firewood that's already there was probably brought by A.

- "There's firewood under [B's] body, suggesting that he was carrying it at the time of death and fell on top of it after getting hit." B was only just bringing his firewood to the campsite when he was attacked.

- "E and F [...] pretty much can't lift more than their backpacks," so it doesn't look like either of them was the one to hit B with a chunk of wood hard enough to kill him.

- The campsite bears "no major signs of struggle", so we can assume B was killed there and C and D were knocked out there, probably by the same person (using the same lump of wood, perhaps).

- A and B are best friends, so we can assume neither of them killed each other.

All of this serves to prove that

>! **B must have been killed by G**. A, C, D, E, F have been eliminated above, and we can assume you are innocent rather than being an [unreliable narrator](http://en.wikipedia.org/wiki/Unreliable_narrator). This also fits with G being "prone to violence, and [getting] upset at the weirdest things." He had the opportunity to do the deed when he claimed to be pissing.