Actually, Brutal Doom is a very new thing, i believe it was released for the public in... 2012? Something like that. It also bears the awesome title of "best goddamn mod i ever played for any game, period". It is so good that me and my brother, playing co-op via Zandronum (a source port), keep seeking out new megawads to beat after we finish the one we have at hand. Our list is getting pretty long, and we're not tired yet. :U (also, it's notable that two doomguys with miniguns set to maximum fuck can actually stunlock a cyberdemon to death)
Also, ogod Heretic and Hexen, both Hexens. Good times! The only thing that bothers me about Hexen 2 is that it's ridiculously hard to navigate properly, what with the complete lack of objective markers and such.
Oh yeah, and Dungeon Siege, if it counts for retro (but if the DS does then goddamn Dungeon Siege is retro too). Fairly simple gameplay, but there's just something enjoyable about it. Must be the loot doing that. :U