The Gold Source (GoldSRC) mod ‘Half-Life Gold‘ is a mod that aims to bring back the “good, old Half-Life 1 of 1998 with better graphic elements”. The mod is split into two parts, ‘Half-Life Gold Singleplayer’ and ‘Half-Life Gold Death Match’, the former of which (the single-player component) was just released. Go and play it now, if you want your nostalgia tickled!
However, Crowbar91 (lead on the project) requires your help. Overhauling the graphics in an entire game isn’t easy, and he is now looking for a team to help him finish the Death Match component of the game, and also possibly start two other projects, ‘Opposing Force: Gold’ and ‘Blue Shift: Gold’. Check out the Mod DB age to see if you can help.