"You mean Bob, the accountant, who was with you when the first murder happened and has rock solid alibis for the second?"
"...yes"
"ok. How do you explain those two things?"
"... nevermind "
Or like, "we think he's a shape shifter!"
"So remember in session 0 we established this is a modern day, no magic, realistic setting?"
"...no."
"Ok, well, we did, and it's in the setting document pinned in the channel. Shape shifters don't fall under realistic, modern day, no magic, so they don't exist in this game."
I was wondering for a quick minute there why you'd play in a physical channel before I remembered that not everyone is as privileged and lucky to play in person all the time.
I like using one I only remember from my dad when I was a kid and I don't know where it came from, nor have I ever seen it used in popular media the way others have, like the two doors/liar puzzle or the weighted jug one.
It involves two gold ropes hanging from rings in the ceiling which is high enough to die from should you fall. The puzzle requires obtaining both lengths of rope without dying. I can't remember the whole thing off-hand (I have it written down, physically in a notebook; but it's still in a box buried in a closet right now). It's such a convoluted puzzle that if I hadn't written the whole thing, and the solution down, I can't remember it and would never be able to solve it if I ran into it.
Edit: I have dug out the notebook and found the riddle for y'all. I almost had it right in my head when I made the comment, but psyched myself out lol
There are two lengths of rope made of a magical gold alloy, attached by rings in the ceiling about 1 foot apart from each other. The ropes are pretty thick, but still able to be climbed without assistance. The rings are 108 feet from the ceiling, and there is a special knife on a nearby pedestal that can cut through the ropes without effort.
The goal is to try and obtain as much hold rope as possible; but how does one do it?
Answer:
The solution to get 100% of both ropes is to tie the ends of the ropes together at the bottom, climb up and cut 1 rope free of its ring. You then pull that rope through the ring of the remaining rope until the knot from the bottom ends that are tied together is just past the ring, grab the loose rope to support your weight while you cut the second rope and then shimmy down holding both sides of the rope, and once at the bottom, you just pull both ropes free of the ring. This is easier to demonstrate with a physical mock-up, which is pretty easy to do with some key rings, styrofoam blocks and twine.
I find it fun to use because even a failure can technically yield a reward, just not as much of one if the only reward is the rope and knife itself.
I once made a home base for an elusive magic artist that is notorious for making really powerful magical artifacts with shitty side effects. Shield of Biting that bites the user, invisible invisibility cloak, Rhythm Heaven's Monkey Watch, a dagger that berates the user on misses, one puzzle that I found online that stumped the party for hours.
So I made it a base with annoying puzzles. I had solutions for four out of five of them, then decided, "Eh, they'll come up with something eventually." They did the other puzzles first though, so they just came up with a solution that fits the theme.
It worked.