The Top 7... alien invasions

Gears of War got us thinking: Massive explosions. Guts strewn everywhere. People running in terror. Few things ignite the minds of gamers like a good alien invasion. It may be bizarre or terrifying (and in the case of Gears of War, it may come from underground instead of outer space) but in video games, aliens always bring massive destruction in their wake. This week, we take a look back at the seven games with the most memorable, exciting or disturbing alien invasions... ever.

7. Halo 2 (2004, Xbox)

If you've played Halo 2, you've already encountered the brilliance of the game's early Earth invasion levels. While huge parts of the game take place in space - and revolve around Master Chief taking the fight to the Covenant and exploring a new Halo - there's that fantastic sequence: the city, crawling with Covenant, with giant walkers and battle raging all around, vehicles to steal and general havoc to enjoy. It's a thrilling moment that's utterly different in feel from much of the rest of the game, and really lends a whole new perspective to the human struggle against the Covenant.