Lantern of in-sight: causes any object or entity you're aware of and can keep a direct line of sight on to glow as bright as a non magical lantern. The lantern itself does not produce light. Had a player use it to highlight someone hiding in a crowd when the party failed to see them.
Jewel of Becoming: when activated the player became a gemstone for 1d6 hours. The rogue ended up exploiting this heavily by becoming a jewel and either having another player sell her or just being in the path of someone. Once she turned back she'd rob them blind and sneak out back to the party.
Immovable ladder: it was a rope ladder but the rungs in the middle and either end were immovable rods. This one the artificer cobbled together in game and I allowed for it. They spent a lot of time trying to figure out how to use it for more than a reliable way down from a second floor but never did manage anything wild. They couldn't even really use it to go up because someone would still and go climb up there to set the top rod.
Maxwell's Morning Tonic: a bitter, dark, and slightly oily potion that when drank, counts as a short rest or turns a short rest into a long rest. It also gives you a -1d6 to hit and sleight of hand.
It's just a strong coffee.
We played it as the rogue would destroy the box in returning to normal size, but they take damage equal to the boxes health before it explodes.
My favorite situations were her getting trapped in a floor safe for an entire fight because the bandit immediately locked up the pretty stone, her erupting out of the pocket of a maid being interrogated for stealing from the Lord, and her exploding from a coin purse on a Duke nearly a county over because the he picked her up while leaving the bank instead of while entering.
I'm not sure how Immovable Rods work exactly, but presumably with three of them you could place two, stand on them, place the third at some reasonable height, move the first two to a new location and repeat as needed, then once at the appropriate height, "lock" the top rung and use the ladder proper to climb back down, setting the other immovable rungs as needed.
That's an idea, but the rods had 4 rungs between them that were just wood so they were about 6ft apart. They had used it by setting the bottom, having someone tall put the middle at full length away, then have that person climb up and balance on the top rung to then set the next one at full length. It often led to hilarious critical fails on the balance checks.
I'm genuinely surprised no one thought to hold them in place with a 10ft pole, that's d&d 101 right there.