I like giving my group puzzles and I often browse there for inspiration so I thought I'd share one I came up with that went down well with my group. This particular one was inspired by similar puzzle from Critical Role, however, it is different enough that even though a few of the group watch the show they didn't figure it out based on the episode.

The puzzle was at the entrance to a Thieves guild hideout, as such it revolved around being able to read Thieves' cant for the clues and picking the locks, however it can easily be adapted to another theme.

The puzzle: A solid steel door blocks the passageway. It is heavily reinforced and does not look like it could be forced open. The door has 5 heavy set locks, each seems identical and evenly spaced from one another. The only thing that sets each of them apart is a series of characters engraved into the steel next to each lock.

(Here I checked to see if the PCs could read any of the messages, baring in mind that first 3 languages all share the same alphabet so being able to read one of them meant that they could identify the numbers)

The first lock's message is in Dwarvish it says: 2 or 4

The second lock's message is in Goblin it says: 1 or 4 or 5

The third lock's message is in Orcish it says: 6

The forth lock's message is in Common it says: 3

The final lock's message is in Elven it says: 1 or 2 or 4

The door as some additional information on it that is revealed with a simple investigation. In Thieves' cant at the top of the door a message reads:

"Pick in order or not at all"

The 2nd and 3rd locks have additional information next to them, also in Thieves' cant:

Next to the second lock reads the message: "Never trust a Goblin"

Next to the third lock reads the message: "Orcs can't count"

Investigating the locks shows that they are rather heavily scratched around the keyholes, and have pretty simple locking mechanisms, requiring little skill to pick.

It is also pretty obvious while investigating the door that it is heavily trapped, there are a number of small pitted openings around the door's frame that appear designed to release something.. unhealthy.. i was going to go with a 6d6 poison cloud.

The idea being that the PCs pick the locks in the correct order or the door's trap goes off.

Solution The correct combination based on the clues is: Lock 5, Lock 2, Lock 4, Lock 1, then Lock 3.

It's pretty simple and the actual puzzle only took the group a few minutes but you can add complexity as you see fit. One thing that made this particularly fun was that only 2 of the group went down the tunnel and between them neither understood Dwarvish or Elven. As a result the group played a sort of pictionary for 20 minutes as they tried to relay how the symbols looked (taken ones I quickly sketched) to the resident linguist in the group via Sending Stone. It's the unexpected outcomes that make this game great..