Sid Meier's Alpha Centauri (thing)

Wonderful strategy game in the vein of civilisation (duh!) What sets this apart in my mind are the different factions you can play:

• Gaia's Stepdaughters
• The Human Hive
• The University of Planet
• Morgan Industries
• The Spartan Federation
• The Lord's Believers
• The Peacekeeping Forces

An expansion pack for the game, Alien Crossfire, added new factions:

• The Cybernetic Consciousness
• The Nautilus Pirates
• The Free Drones
• The Data Angels
• The Cult of Planet
• The Manifold Caretakers
• The Manifold Usurpers

Alien crossfire also added new native life to the list:

• Xenofungus
• Mind Worms
• Isle of the Deep
• Locusts of Chiron
• Fungal Towers
• Spore Launchers
• Sealurks