the book of unwritten tales (all 3 games)
deponia
edna and harvey

Black Mirror Is a good oldie. Its even on steam! ^^

The Dark Eye: Chains of Satinav and Memoria are one of the best I've played recently.

Daedalic Entertainment is a pretty good company for these kind of games

LucasArts adventures:
The Dig
Full Throttle
Sam and Max: Hit the Road
Day of the Tentacle
Grim Fandango
Loom

Others adventures:
Beneath a Steel Sky
The Legend of Kyrandia 1, 2, 3
Syberia 1, 2
Broken Sword
The Flight of the Amazon Queen
Black Mirror
Runaway
The Longest Journey
Machinarium

Anna's Quest

simon the sorcerer 1 & 2 (the 3d is sh1t, and didnt play the last one) Discworld 1 & 2 ( you have Discworld Noir, but i didnt like it) Maniac Mansion (you can play it in Day of the Tentacle xD) Gabriel Knight also the leisure larry saga is kinda funny

Sam & Max
Edna & Harvey
Grim Fandango Remastered
The Book of Unwritten Tales
Back to the Future: The Game
Sherlock Holmes: Crimes and Punishments
Detective Grimoire
The Secret of Monkey Island: Special Edition
Syberia
The Tiny Bang Story
Technobabylon

Back to the Future: The Game
Beneath a Steel Sky
The Blackwell series
The Book of Unwritten Tales
The Deponia trilogy
Edna & Harvey: The Breakout and Harvey's New Eyes
The Flight of the Amazon Queen
Gray Matter
The Journey Down
The King's Quest series
The Leisure Suit Larry series
Telltale's Sam & Max series
The Space Quest series
Strong Bad's Cool Game for Attractive People
The Zork series

Grim Fandango is my favorite game ever. The original Gabriel Knight game on GoG.com is a classic, with great voice acting (Mark Hamill, Tim Curry, Leah Remini, Michael Dorn). Heck, any of the old Lucasarts Adventure games are a good bet.

Anything from here

Everyone has said pretty much everything now, but I'd like to give my very special recommendation in case you get your hands in a Playstation or Sega Saturn: Blazing Dragons

I have a lot of point and click games that I haven't played yet, but out of the ones I have played, I liked these the most:

The Longest Journey
The Whispered World
Edna and Harvey: Harvey's New Eyes
Machinarium
Harvester
Still Life (not Still Life 2 or Post Mortem, neither of those games were that good)

Edit: I also enjoyed Torin's Passage a lot, but that may be more to do with nostalgia since it was one of the first point and click games I ever played. Then again, most classic Sierra games are good.

Zak McKracken and the Alien Mindbenders :)

Adding to what was already mentioned:
The Shivah
The Samaritan Paradox

Assuming you know the classics already, everything by Wadjet Eye (except maybe Puzzlebots).

Myst and The Longest Journey are my all time favourites.

Legend Of Kyrandia (all three parts- but my favorite is Part 2 - Hand Of Fate)
You need to try them!

Also:
Toonstruck
So Blonde (tries to mimic Monkey Island... doesn't succeed but still cute)
Flight of the Amazon Queen

i enjoyed morningstar: descent to deadrock. It was bundled so if you didnt get it you can find it for cheap trading

Jolly Rover, it's the game that made me love point and click adventure games, it made me realize that this genre is quite awesome and I was wrong not trying it out for so long.

The deponia trilogy was amazing.
The night of the rabbit has a slow start, but the game is quite a long and fun point and click adventure game.

I have many point and click games on steam, I should start them someday. Someday.