JTCOTE?
One game I had difficulty on, even with a walkthrough, was Beneath a Steel Sky. I kept getting tripped up on one puzzle, and even reading all the hints *and* the walkthrough, I still couldn't figure out what I was doing wrong. After a bit of thinking, and trial and error, it turns out that there was another (unrelated, mind you) scene I needed to trigger first, that neither the hints nor the walkthrough mentioned as being necessary to do first. Thankfully the rest of the puzzles in the game were pretty logical.
Peace & Luv, Liz