Shoggoths

Shoggoths are possibly Lovecraft's most popular non-deity monsters. They have amorphous forms and are nigh on unkillable.

In the RPG...

Shoggoths are amorphous death machines. Their attack is pretty much an instant kill for any target, and it gets two of them per round, each with a 70% attack chance. Even more nasty is that they can engulf a victim, who can suffers an instant death if they lose an opposed STR roll against the Shoggoth's 315 STR. There is a 95% chance this will happen, though surviving wouldn't make much difference considering that, while engulfed, victims are subject to the same damage as a regular attack—so most likely an instant death anyway. Their STR is divided by the number of victims, as is the damage, but I think that's a very small consolation. Say there are four victims, that's still only a 24% chance of not dying instantly. And there is not even any mention of being able to escape, so I guess that's not an option.

    If the Investigator's manage to not get eaten, they have little chance of hurting the thing anyway. Fire and electrical attacks are halved, physical weapons do only 1 damage per hit, and it regenerates 2 hit-points per round. Basically, no one is walking away from a shoggoth encounter.

In a video game...

There was actually a Shoggoth in the video game Call of Cthulhu: Dark Corners of the Earth. However, it must have been drugged or something because it was no threat at all. The player could literally walk around it and would only take damage if they accidentally touched it. Because of their amorphousness, I imagine an active, mobile Shoggoth would be pretty much impossible to create in a game. I think they'd be more likely to work in a pre-animated set-piece.

In a film...

Like pretty much every Lovecraft fan, I'm waiting for the day someone adapts At the Mountains of Madness, where we'll get to see Elder Things, giant penguins, and of course, a Shoggoth. Guillermo Del Toro was planning to years ago, but that all seems to have evaporated now, which is a shame because he's one of my favourite Directors.