Star Wars: Return of the Jedi. Chewie and the piece of meat. Possibly one of the few instances where it was bait. Annoying for those who thought Chewie should've been too smart to fall for something so obvious. Admiral Ackbar would have known better.
Mom and Dad Save the World has the Schmuck Bait of the "Light Grenade" which will vaporize anybody who picks it up. When the protagonist asks why anybody would do such a thing, he is shown the ingenious inscription, "Pick Me Up". This is a Planet of Schmucks. The grenade manages to wipe out a whole squad of soldiers one by one.
With the last soldier in the squad calling for more men.
Joe Versus The Volcano. Joe always wondered what the valve labeled "Do not turn" would do if he turned it. Since he's dying anyway, he goes right up to it and gives it a good turn. Absolutely nothing happens. Joe is incredulous about it. Why have a sign if nothing happens?!
The Fifth Element: Zorg counts on this happening to his alien former henchmen after giving them some weapons: "Now a real killer, when he picked up the ZF-1, would've immediately asked about the little red button on the bottom of the gun." One of the aliens looks puzzled at the button and then presses it, blowing them all up.
The Transporter: Rule Three: Never look in the package. Too bad said package got noisy...
It is at its worst in Ringu, where the protagonist actually has to travel to the Izu peninsula campsite and ask the owner for it, while being warned, and then watches it anyway. And leaves it where her kid can get at it.
While robbing a gumball factory, one of the thieves cannot resist the door labeled "DO NOT OPEN THIS DOOR" in The Brink's Job.
Constantine. While the title character is preparing to drag the demon out of the possessed girl he tells the men helping him "Close your eyes. And whatever happens, don't look." One of them does. He collapses and his hair turns white.
In Saw II, Jigsaw leaves his victims a note specifically instructing them not to use the key found within on the door to the room. Someone does it anyway and ends up shot by a gun positioned in the peephole.
In Con Air, U.S. Marshal Larkin and a couple of prison guards search Big Bad Cyrus Grissom's cell. One of the items they find is a small package with a note taped to it reading, "Do Not Open." The Genre Savvy Larkin immediately leaves to call the bomb squad, cautioning the guards on the way out not to open the box. He's barely ten feet away from the cell when one of the guards plops down on the cot and opens the box. Cue massive explosion.
Time Bandits: "Mum, Dad, it's evil! Don't touch it!" Guess what Mum and Dad proceed to do?
In The Cabin in the Woods the cabin's cellar doesn't just have one piece of Schmuck bait, oh no. It's filled with dozens of weird or mysterious objects, and, if played with, each of them will summon a different kind of monster to kill the cabin dwellers.
A couple of the gags in the Home Alone films follow this principle. For example, one involves the crook pulling on a doorknob, only to find that it comes loose and is attached to a string. He then must keep pulling several more yards of the string before the trap (a staple gun at crotch height) is triggered. Presumably the idea was they he'd know something was up, but be too determined to figure it out to stop.
A similar one has the doorknob cause a large tool chest to start rolling down the stairs at the door. The sound is extremely loud, and it takes several seconds for it to complete the journey. Naturally the trap requires that the thieves be curious about the noise and press their ears against the door, until the tool chest arrives.
Both of those are from Home Alone 2; no particularly obvious traps are in the first one, except perhaps after Kevin uses his BB gun to shoot Harry in the crotch through the doggy door. Then Marv sticks his head through the door, and is promptly shot in the forehead.
Unthinkable involves the brutal torture of a man who has made several nuclear devices and placed them in cities across America. After one of the interrogators begs him to give them evidence that the threat is real, he relents and gives them a location. The building matches one of the video recordings he had sent to the government, but there is no bomb. Instead, on the roof is a picture of himself taped to the wall. Everyone leaves it alone until one dumbass soldier blurts "What the hell is that?" and snatches the picture off...triggering the detonator it was covering and blowing up the shopping mall across the street.
The protagonist in Hellraiser: Deader finds the several day old corpse of a young woman with a packet near her body and the LamentConfiguration in her stiffened hand. After retrieving both, the journalist watched a video tape from the packet in which the dead woman instructs her, with quite a large degree of urgency, to not open the box. Mere seconds after finishing the tape, she opens the box.
In the climax of Steel the Big Bad has the hero's hammer. Steel tells him not to press the red switch. The big bad notes he "has to push the envelope", activating the electromagnet and causing the weapon to return to Steel.
Deathstalker: The Amulet of Life is sort of used as this towards the end of the movie. It is left hanging from the ceiling of a completely unguarded room that the main protagonist had no trouble reaching. When Deathstalker tries to grab it, however, one of the main villain's mooks attacks him.