Obsidian Conflict is a cooperative multiplayer modification set in the Half-Life 2 universe. It features a large amount of new gameplay features on all-new maps specially designed for the mod with focus on cooperative gameplay, as well as over hundred user-made maps following the same formula. In addition to that, You're able to play through vanilla Half-Life 2 all the way up to Episode 2, as well as experimental support for cooperative Half-Life: Source play.
Merchants allow you to purchase weapons and equipment by using your score.
But not only weapons, on some maps you can even buy more or less useful, even pointless stuff like hats or a package of Kellogg's, its all up to the mapper.
that makes roleplaying in obsidian to the best thing :)