Well, it all started when Doom came out with an option where you can play against another human player. DeathMatch was born! But then soon shortly after, the Doom clones came and they to had DeathMatch.
Duke Nukem 3D had great multi-player, it was very interactive. Like you could turn on tanks and start missile launchers. The downside was that some weapons were, well too childish. Like the "Freeze Ray" and "Shrink Ray". Pretty lame weapons.
ID Software later made the ultimate game that changed all 3D shooters forever, Quake. Quake had a very strong deathmatch with unique weapons such as "The Thunderbolt" and the two "Nail Guns" These guns were more realistic then Duke Nukem's, but Duke edged out Quake in one thing: interactivity. You barely can do anything in Quake! Yes, you might hit a switch here or there but not too many maps were like that :-(
People still wanted to practice at home but didn't want to go online or hook up LAN. The answer: BOTS. Bots have very smart AI and you feel like your playing humans even though your playing the computer.
Luckilly, Team Fortress, a Quake MOD came out and took a further step in Quake. This MOD is one of the more famous MODS out there and still is played today.
Quake's sequel later came out, Quake II. It's multi-player improved, but the weapons weren't really realistic. It felt well, too futuristic. Some people might like these weapons such as "The Railgun" and the "Hyper Blaster". QuakeII's BOTS were more human like in this game, such as they ran away when they knew that you had a better gun then them or they would jump when a grenade is near.
Then an incredible QuakeII clone came out, Unreal. Unreal's weapons were probably they best weapons anyone has ever seen, the problem was that the LAG was too high and that turned away many people. What's good is that Unreal had many modes to chose from like "King of the Hill" and "Dark Match"
As multi-player grew better and better, each game had it's own attributes. Duke Nukem had the best interactivity. QuakeII had the most servers, and less ping. Unreal had the best weapons. Only one game had all three of these...
Half-Life. Probably the biggest game of the decade. It had very well made maps, the weapons were very realistic too. They also had a neat "Spray-Paint" feature where you can sort of mark your territory. You can also create your own Spray-Paint image too. Half-Life had Duke Nukem's interactivity, QuakeII's server count and Unreal's incredible weapons. At this site you'll find some DeathMatch maps of Half-Life and you'll see the weapons in a multi-player perspective.