Penumbra is very funny.

[Googolplex]

@Brute
I think, weapons make the game even more dangerous and innovative. But I mean not guns or laser-swords for superheros. I mean an old rusty hammer or a pickaxe like in Penumbra. This weapons aren't really suitable to fight. And the game's goal is not to kill enemies. You have only the option to fight them if you can. And you can't kill them easy, it is very hard so that you maybe don't try to fight.
This weapons should be more tools as for fighting. But it's better than no weapons. And it's even better, when you get weapons in the beginning and lose them during the game so that you suddenly haven't weapons anymore. Then you are even more frustrated in fear. And that makes Penumbra perfectly.
The atmosphere in Penumbra is even more dangerous as in Amnesia. Amnesia only have more horror elements, but Penumbra is more oppressive. And Penumbra did not want to kill the enemies, you can try it, but it is recommend to run away or to hide behind a box. It have weapons, but mainly not for fighting.
If a game have no weapons, it will be less complex, you only have to hide.
The weapons in Penumbra can be used more to crush through fences for solving puzzles. To have weapons is a good feature, when it is like Penumbra, where you can't kill the enemys (nobody can kill all spiders).
It gives the game more horror feeling.
But strong weapons will destroy all horror feeling.