3. Discworld 1 & 2
Now, I actuallydid beat the Discworld games, however, I was forced to use a guide with such regularity that I honestly may as well have just read the script. Discworld's puzzles are, to put it mildly, hair-tearingly impossible, requiring you to connect gaps in logic so wide they make the Grand Canyon look like a crack in the asphalt. I don't know of anyone who managed to beat either of the original Discworld games without consulting the walkthrough once every 5 minutes; if you managed it yourself, I imagine you probably register on the Autistic spectrum.