Hi i'm after some good point and click puzzle games. Here's what I have played and really like

Gobliiins
Ween: the prophecy (my favourite)
Shadowgate
Machinarium (not a retro game but still)
Monkey Island

What I'm looking for is a good challenge, but not too challenging (like Myst). I hate the Hidden Object style games, annoying!
What I like about most of these games is not only the challenge but the darker tones in some titles, (ie Shadowgate and Ween).

Any suggestions? Cheers guys