Welcome to the Firearms 2.4 and 2.5 gameplay mix compilation special! Sorry about the aspect ratio (my editor is terrible at dealing with 16:10 clips)!
Introduced in April of 2000, Firearms is one of the classic mods for Half-Life (1998) that demands team play and a somewhat tactical approach in running and gunning.
Instead of a currency system like that of Counter-Strike, Firearms gives each player a set amount of credits to spend on armor, equipment and weapons. The amount of credits you spend on the former two categories determine what guns you can afford and how many you can carry (only limited by credits). Of course, you can also choose from pre-determined classes or even to not spend anything if you so desire!
Even before Battlefield 1942 popularized its conquest-style multiplayer game-mechanics in 2002, Firearms used a reinforcement system for tracking which team is winning or losing a match since the beginning. Starting from version 2.1 (summer of 2000), a skill system was added to the mod for added depth and class customization. This not only extended on the offensive options, but also expanded the reinforcement system to accommodate gaining back lost reinforcements via means of evacuating fallen soldiers (MEDIVAC) as a medic, incentivizing more aggressive teamwork to keep your numbers higher.