Besides all LucasArts Adventures I would recommend:
Kyrandia 1 - 3 (play these!)
Simon the Sorcerer 1 & 2,
Inherit the earth,
Toonstruck (that one was very great indeed, it's a shame the sequel has been canceled!),
Discworld 1 & 2,
Chewy - Escape from F5,
"It's a great day for spitting!"