11. Halo
You must experience: The Silent Cartographer level... and punching a Grunt right in the face. Although you can point to Halo 2 as the one that kickstarted the online revolution with its perfect matchmaking multiplayer, it's this first instalment that still has the best set of levels, introduction to the mythos - and just as a piece of gaming history you don't ever want to be caught short admitting you've "never played Halo". Single-handedly proving shooters could work on consoles in a big way, Bungie weren't content with just nailing obvious things like the aiming and feel of movement - instead it was with the introduction of vehicles like the multiplayer-baiting Warthog, flying death-from-above Banshee or gargantuan power fantasy-enacting Scorpion that were the icing on the cake.