I think I've mentioned it before in some other thread, and it's not strictly an adventure game, but in the old Amiga classic
Metal Mutant I was stuck for ages in one particular spot.
Your character can change into three different robotic forms (humanoid, R2D2-type, and dinosaur with supplementary remote-control fly), and each form has multiple capabilities, so there's always the question of which form and which capability will do the job at hand.
In this particular room you are practically nose-to-nose with an enemy that breathes fire or plasma or something at you. There is just enough time to change to dino-form and switch on the dinosaur's force field shield. (ooh) The problem is that you can't do anything but stand still while the shield is on, and as soon as you turn it off you get fried. All you can do is release your tiny remote-control fly, but all that can do is fly around.
It was my husband, Colin, who said:
Spoiler:"What's that little thing up there on the wall?" Yep, it was a switch, a tiny button. Press it with the fly, the floor opens up beneath the enemy, and that's that.
Col's never let me forget that he solved that one. Especially since he's not even interested in games.
