What to choose?

The Walking Dead, of course.

6x Fortix. Of course.

You will get the best value from Max Payne imo longest play time and a fun game

How about between these 2, don't starve or spelunky? I want to buy one but don't know which.

Max Payne 3.

The Walking Dead, played it almost nonstop for 2 days and loved it to bits.

buy all of them

The Walking Dead is bundled so you'll probably can get it cheaper, but then again you have steam wallet.

My vote goes for Spelunky and Legacy of Kain.

Would not recommend getting Monaco unless you have people to play though it with.

My vote goes to Spelunky.

When in doubt ask strangers on the internet. ;-P

Based solely on a quick scan of your most played games, I voted for Max Payne 3.

My personal choice would be Spelunky for overall value.