It all started with the Half-Life MOD aptly named "Firearms" which is in the same vein as Counterstrike, except I dare say more realistic and focusing on a combat/military setting rather then a counter-terrorism/swat setting. Selection menu had a nice (and accurate!) description of each weapon, from a Beretta M9 to the G3 "Volmer" machine-gun-thing (MP5 in .308 with a 50 round belt anyone?!) to the famed FAMAS "railgun", to an M60 and even a Saiga-12k. Also, unlike CS you actually had to think of your loadout, since your weight was restricted. Wanted to tote a M60? Well, gotta give up on armor protection and forget a sidearm. Want to walk around in a full suit of Level IV armor? Well have fun with only being able to carry an MP5, and so forth.