I recently got a $20 steam gift card and I'm looking for a new game, it doesn't have to be a 20$ game, I'm willing to spend extra. I'm looking for something with a lot of replayability and high difficulty either from challenging gameplay or punishing game mechanics. I tend to quickly lose interest in a game if losing isn't a strong possibility. To give you some idea of games I've liked and still play and to make some sort of recommendations for others while at it, here's a list:
The Souls series(demon's souls, dark souls, DS2)
Monster Hunter Series(been at it since the original and love long boss fights where one or two hits could end it)
Front Mission series(one of the few tactical RPG's I found challenging which didn't boil down to rock-paper-scissors)
Armored Core series(or anything game with lots of customization with challenging gameplay)
Mechwarrior Mercenaries(I love the management aspect and how your performance directly affected you since taking too much damage could render your mechs unavailable for some time and cause monetary loss) If anyone finds me something with this kind of punishing management system on top of an action-based gameplay I will forever love you
Many roguelikes(the ones not overly focused on random unavoidable stuff as the main source of death, I love Cataclysm DDA and ToME)
AI War(oh I love how this game never fails to be hard no matter how good you get, winning the game on the highest difficulty without extreme cheesing is considered a bug)
Way of the Samurai series(pretty challenging combat system)
Creative games with actual gameplay purpose for your creations(looking at you space engineers >:| ) where your designs matter(From the Depths, Reassembly, Windforge...)
Games with some degree of simulation or an advanced damage system where taking damage has lasting consequences.(War Thunder, Silent hunter, Mechwarrior, various games where you create designs and have parts damaged/destroyed)
I'm a glutton for sadistic difficulty, but i'm not really into those platformer games like vvvvv, iwbtg, super meat boy, and the other dozen of other games like them. I did love Cave Story though.
I am a huge sucker for complex build-crafting in games and can spend hours having fun not playing the game but just coming up with builds.
Anyone got any games on steam to recommend, both recent or older titles I might have forgotten about?