So I loved the idea in this thread. I think it's a nice idea to play games that you've never wanted to play before, and I want to repeat it with me.

The rules: You see what games I haven't played yet here. Then you post the one you think I should play here in the comments. I'll make a list with the first 20 suggestions; those will be the games I will play, and later make a mini-review of them.

Only suggest games that I haven't played but I've got.

Credit for the idea goes to ageofarmageddon :D

List:

1) Ironclads games - suggested by DackXYZ

I'm unhappy with these. Ironclads: High Seas didn't launch, neither did Schleswig War 1864. Weird, because my computer meets the minimum requirements... don't know what to think.

2) Cave Story+ - suggested by kanga the rooster

I really enjoyed playing this game. From the beautiful pixel art and the 16-bit music, to the Metroidvania style, and the lovely characters. There are lots of moments that make you like the characters, like this and this other one.
Bad things appeared very soon into the game, as I got a map, but didn't know how to use it. Controls aren't well explained; I had to look for them in a website.
There's a high amount of achievements that make the game longer, experience points, levels, powers, lots of items, cool boss fights and other things that are common in Metroidvanias.
So, my conclusion is: this game is awesome. It was in the last Humble Bundle, so there are lots of people who have it but haven't tried it yet (like me some hours ago). Give it a try; you've got nothing to lose.

3) The Ship Singleplayer - suggested by algiesha828

4) Don't Starve - suggested by me, can't wait to play that awesome looking game!

5) Worms - suggested by Cha0sSt0rm

6) Hitman: Blood Money - suggested by bibboorton

7) Revelations 2012 - suggested by zelghadis

8) Waking Mars - suggested by GristlyKingster

9) Company of Heroes - suggested by gonsi

10) Commandos: Beyond The Call of Duty - suggested by RotiKering

11) Broken Sword games - suggested by Julianne

12) Ceville - suggested by FogFrog

13) Codename: Gordon - suggested by Caerbannog

14) Hinterland - suggested by Azelka

15) World of Goo - suggested by ageofarmaggedon