Halo 3 has probably been one of my favorite FPS games of all time. My favorite map that I played endlessly was Valhalla in multiplayer. My friends and I would stay up all night in online matchmaking and we'd cheer when we got this map every time.
But what is Valhalla?
It was a spinoff of Blood Gulch in the original Halo. However, Valhalla is a forest-y valley nestled into the base of two giant mountain cliffs, with large hills, and a waterfall that leads to a River that runs down the center of the map and into the ocean on one side of the map. One side of the map has the ocean and the other side has a cliffside. The setting seems to be mid-day and has a very free, open feel. Each side of the map has a base that each player team starts from.
Inside this base there are several guns, lift pads that launch players out into the valleys, and vehicles such as the Mongoose, Warthog, Wraith and the Banshee.
There are also other power-ups available such as the Bubble-Shield, and power drain.
Players can snake through their bases, or they can rush head first into combat via the gravity lifts present in the area where they spawn in their bases:
What I like about this level is that it gives players a choice: Meet head on in the center, or pick up a long range weapon like the battle rifle or the Sniper rifle (or spartan lazer!) and pick people off. Strategies revolve often around the vehicles, whatever power-ups are available, and what weapons you pick up. Game modes range from capture and hold to juggernaut to team deathmatch.