Rat Race

Rat Race is a multiplayer map in Halo: Combat Evolved and in Halo: Custom Edition.

Summary
It is a sort of circular map, with a multitude of Teleporters, tunnels and passages.

The most notable feature of the map is the central section of elevated tunnels. There are two entrances to this complex, one by a teleporter and one by an inclined ramp. The strategic value lies in the two exit points which allow a player to drop unexpectedly from the ceiling through a wide hole into the enemy section of the base. Since this is strictly a one-way vector of attack and jumping down this hole usually entails grabbing an active camouflage or Overshield power-up, defenders are forced to keep an eye to the ceiling.

Although the Bungie.net description claims that it is a UNSC attempt to mine into the surface of a section of Halo Installation 04, the fact that they had only 2 or 3 days to set it up makes it difficult to confirm with known facts. Likewise, it is not known where they would have found the equipment necessary, or the time to do this.

Capture the Flag

 * First, if located on the "base" (there are no buildings in Rat Race, only the flags) that has the Flamethrower, get it. It is the best weapon in the entire map.
 * If you're at the enemy base, do not act miserly and only chuck one grenade, they will spawn there, and your grenades will either weaken them to the extent that you can finish 'em off with any weapon or if playing on 50% or no shields, kill them.
 * If you have frags, drain those up before employing the plasma counterparts, they are much more destructive unless you manage to "stick" an opponent.
 * Before charging to the enemy flag, keep an eye at the ceiling. There should be either an overshield or an active camouflage, both of which are priceless assets.
 * Go through the tunnel towards the enemy base, and you should be provided with an ideal spot to jump down to retrieve the flag as your opponents will not see you unless you jump down.

King of the Hill (Team)

 * You can spam grenades to either hold off your enemies or confuse them.
 * If it is in an open area, the hill will become extended. Therefore, you should be wary of hiding locations that are crouching and silent opponent might be able to use and evade detection (giving the other team time).
 * At close range, an expert SPARTAN wielding a shotgun is arguably the most perilous one. If given the chance, always take it. If possible, get a plasma rifle to take down his shields and a single shot from the shotgun to send him to Hades.
 * To counter a shotgunner, you can either spam grenades, snipe him (you might require a reasonably distant range and skill) or use the fire-melee tactic from the Assault Rifle.

Trivia

 * The structure of the level resembles a parking lot's up and down ramps, careening off expressways.
 * Other than Longest, it is the only map in Halo: CE that lacks the sniper rifle (even though the sniper rifle is a useless weapon in this map).
 * You can knock down either the Active Camouflage or Overshield by shooting them.