Like forcing the players into an encounter where all their toolkits are nerfed. Close quarters for casters, magical monsters that can’t be harmed by melee, or NPCs that are way OP for the group and they stick to the Monster Manual to the letter.

When I GM, it depends on just how narrow and just how powerful your particular toolkit is. I'm not going to ensure that you can do whatever your thing is at absolutely every opportunity, and if your schtick becomes well known, enemies capable of planning will plan around it when feasible. The more narrow your schtick is, the more scenarios you might encounter where it does not apply simply by chance (for example, if you're a flying archer every room in a dungeon won't gain a minimum 30' high ceiling to maximize your use of that). The more disproportionately powerful your schtick is compared to other party members, the more likely I am to specifically come up with occasional scenarios meant to make it not apply so someone else gets to shine.

Sometimes I will signpost something is a very bad idea, and if you do it anyways (or do something else absurdly dangerously foolish) I'm not going to pop up a guard rail to save you at the last moment - retrieving your body from somewhere adrift on the astral and your soul from the gemstone the archdevil you pissed off is keeping in his treasury to try to save you is the next adventure hook.

You encounter a huge, elaborate tome, on a concealed lectern, in a library connected by a hidden door directly off the bedroom of a powerful wizard, you detect magic and get extremely powerful auras of conjuration, transmutation and evocation maybe "I flip it open to a random page and start reading aloud, I'll sound out any words I don't recognize" is not, in fact, a wise decision. The copy of "Words You Mispronounce And Die: A Primer For Apprentice Wizards" you saw on one of the shelves on the way there, the references to a cursed grimoire of terrible power, the book being bound in the skin of an angel covered in burns and scars, etc, etc should have maybe hinted at that.