Online is not the same as LAN, LAN is much easier to implement as bandwidth is not an issue (well it could be, but in practice it isn't).
Just picture, playing online, but playing offline with friends connected to your network or pc.
Ah! thanks for explaining, well, here's a list of LAN games taken straight off Google:
Age of Empires
Age of Empires: Rise of Rome
Age of Empires 2: Age of Kings
Age of Empires 2: The Conquerors
Age of Mythologies
Age of Mythologies: The Titans
Anything Goes
Battlefield: 1942
Battlefield: Vietnam
Battlezone
Battlezone 2
Baulder's Gate
Baulder's Gate 2
Blood
Blood 2
Bomberman
Call of Duty
Capture the Flag
Carmegeddon
Close Combat
Command and Conqure
Command and Conqure: Red Alert
Command and Conqure: Red Alert 2
Command and Conqure: Tiberian Sun
Command and Conqure: Tiberian Sun - Firestorm
Commandos
Counterstrike
Counterstrike: Source
Daikatana
Delta Force
Descent
Descent: Freespace
Descent 2
Descent 3
Diablo
Diablo: Hellfire
Diablo 2
Diablo 2: Lord of Destruction
Dominion
Doom
Doom (Ultimate)
Doom 2: Hell on Earth
Doom 95
Doom 3
Duke Nuk'em 3D
Dune 2000
Dungeon Master
Dungeon Master 2
Dungeon Seige
Far Cry
Flight Commander
Forsaken
Gauntlet 2
Get Medieval
Grand Theft Auto
Grand Theft Auto 2
Half-Life
Half-Life 2
Halo
Halo 2
Hearts
Heretic
Heretic 2
Hexen
Hexen 2
Homeworld
Interstate '76
Kingpin
Magic Carpet
Magic Carpet 2
Mechwarrior
Motocross Madness
Moto Racer 2
Myth: The Fallen Lords
Myth 2: Soulblighter
Myth: Total Codex
Myth 2: Worlds
Myth 3: The Wolf Age
NASCAR Racing 2
Need For Speed 3
Neverwinter Nights
Operation: Flashpoint
Operation: Flashpoint, Cold War Crisis
Operation: Flashpoint, Resistance
Pac Wars 2
Populous 3
Powerslide
Quake
Quake 2
Quake 3: Arena
Rainbow Six
Rainbow Six: Rogue Spear
Rainbow Six: Eagle Watch
Re-Volt
Redline
Redneck Rampage
Secret of Mana
Shogo
Sin
Soldat
Soldier of Fortune
SpecOps
Starcraft
Starsiege
Starsiege: Tribes
Star Trek: Armada
Super Ken Senshi
Tanks 3D
Team Fortress
Team Fortress Classic
Terminal Velocity
Total Annihilation
Tribes
Tribes 2
Turbo Sliders
Unreal
Unreal Tournament 2003
Unreal Tournament 2004
Unreal XMP
Vampire: The Masqurade, Redemption
Viper Racing
Warcraft
Warcraft 2
War Zone 2100
Worms 2
Worms 3D
Worms: Armageddon
Worms: Blast
Worms: Forts Under Seige
Worms: World Party
X-Wing Alliance
X-Wing vs TIE Fighter
Source:
http://www.thealmightyguru.com/Games/Games-LAN.html