Another good, and well-known sniper spot is only accessible via Banshee, Ghost or Spectre.
Good weapons to get as soon as the game starts: rocket launcher, Brute Shot, Sniper Rifle, and battle rifle.
The few close range encounters you will have usually involve preoccupied snipers, which can be assassinated or stuck. There is a Shotgun that spawns, but most players avoid it as it is unnecessary in the mostly distance based game.
The hills (near the Overshield the middle of the map) are another popular sniper spot, as the rocks offer a surplus of cover.
This is a very predictable spot for snipers to run to, though, and as such it is often avoided. Also, you can get there by a really lucky chain superjump that consists of: the Blue Base superjump, then the teleporter superjump, and then the hard one, a superjump in the middle of the way between the sniping spot and the teleporter. It's reachable by a Banshee or by glitching the wall of the map with a Spectre, Ghost Wraith, or, less common, Scorpion.
The most popular feature of this map is the sniper alcove above the blue base, informally called the Sniper Ledge.
The roof is also useful with a hole to drop into the main room, a teleporter, and a sniper rifle. Each has a single main room which contains the flag in CTF matches and bomb in assault matches respectively, as well as a newly added cellar level containing a Banshee and a gravity lift to the main room. The Red and Blue bases are both identical in layout and the weapons that they contain.