They're not really unfinishable, but bugged me for quite some times, for two commercial games.
- Leisure Suit Larry 2
BITD I've played to the very end of the game and the last action isbut every time I typedSpoiler
obvious to make a Molotov cocktail by putting a bag into a bottle,[close]it's a game over.Spoiler
"put bag in bottle"[close]
No matter what I did I was unable to finish the game, until years later when I came across Al Lowe's own site and found out it's a glitch in the parser that the word 'bag' was always recognised as a verb instead of a noun unless you typed something like "the bag" and when I tried this I immediately completed the game.
The problem was, I always just typed commands like "get stuff" and "look bed" and they never failed, but it would fail in the very last command. This glitch had me stuck in the game for at least 15 years! Also BITD there was no convenient places liked the Internet and some friends I had asked said that the command was correct and they could complete the game (probably because they always typed 'the' like Al Lowe himself did). This was so annoying and this glitch was never fixed. - Rex Nebular (a Microprose point and click adventure game)
It's been a while so I couldn't remember details. This game had two modes, Easy and Normal (or was it Hard? didn't remember).
As a first time player I decided to try Easy mode first and... I was stuck in the middle of the game when I had to disarm a bomb (or plant a bomb? I can't remember. Anyway, it's also about BOMBS like in LSL2's case).
I was stuck for maybe a few weeks until I decided to start over and try the Normal mode... and I got through that part readily!
That meant the Easy mode was even harder!
The reason was that in "Easy" mode they removed a number of required actions for the player to make progress, but after such changes, many of the actions were no longer logical.
In the part in question you could never guess that you just needed to jump to the end without doing all the in-between logical steps and I think this was just poor design.