Here I enter the dangerous territory. Similar to my favorite Halo campaigns opinion piece, this is strictly that: MY OPINION. Nobody is really right or wrong, but I believe I've logged in enough hours of each Halo to give a dignified response. So with no further ado:
5. Ascension (Halo 2)
Though a small map in size, Ascension great for snipers. With two towers which showcase the whole map, it's easy to pick apart your opponents. That is unless they are flying the Banshee and racking up kills. One would think that the covenant ship would be a dominating factor on such a small map, but luckily there is a rocket launcher hidden away on the under belly of the map. It's all about patrolling your area and watching you 6 to be victorious.
4. Blood Gultch (Halo Combat Evolved)
Simplicity is the key. Large map,two bases, a couple of ditches and canyons, and some caves and cliffs along the wall. Ideal for Capture the Flag matches and Big Team Slayer (as well as some Forge), Blood Gultch is as classic a map as you can get for a Halo game. It was remade as Coagulation for Halo 2, and served as a major inspiration for Valhalla in Halo 3. It was also remade as a multiplayer map in Halo Wars, and made it's return in Halo: Reach, with a new and hugely expansive playable area outside of the main canyon, and is a main section of Forge World.
3. Ivory Tower (Halo 2)
In the middle of Ivory Tower there is an alley that leads to a waterfall where you will find the Rocket Launcher and many deaths since that's the main rush point in the beginning of games. This alley leads to a circular area with a palm tree sitting at the base of a set of giant stone steps covered with grass. These steps lead up to an elevator and two hallways. One hallway leads to a dark room and the other leads to a lighter room that bears the Overshield. The elevator can either take you to the upper part of the map that has the Sniper Rifle or the lower part of the map where you can acquire the Energy Sword. With so many vantage points, there are countless ways to remain successful on this map.
2. Hang Em' High (Halo: Combat Evolved)
Where many of us learned the ways of Halo, there's no way I can do this list and not include this map. Hang ‘Em High is a medium sized map suited for 4v4 action and is tailored for Slayer. The map is a simple asymmetrical map with multi-leveled buildings on each side of the map. On the first floor, the map is littered with many small blocks which are referred to as Tombstones, and two small shelter structures on either side of the map, and in the center of the map lies a large trench. The second and third levels contain many ramps and bridges that connect both sides of the map and two structures on the top of each side. These catwalks contain some power weapons such as Rocket Launchers and Sniper Rifles.
1. Zanzibar (Halo 2)
Zanzibar contains a large base with an controllable gate, operated by a switch which either team can open, but not close. The gate is a main part of objective based games such as CTF, as a Warthog or other vehicles can be driven through the open gate directly into the base.
Zanzibar is also host to one of the most destructive and interactive areas in Halo 2 multiplayer. The Base that houses the generator sub-systems has two shutter windows to the left of the building, the supports to which can be shot off or hit off with a melee attack and used to prevent fire from entering the second level of the base from the outside. The concrete blocks next to the two forward firing machine guns can be blown off. The large pillars on the first floor of the base next to the flag spawn can be chipped away by gunfire. The windows can be blown out, which can be used to defend whatever you're trying to defend,
One of the unique aspects of Zanzibar is that it supports every type of combat very well. It is good for close-quarters, mid-range, and sniping, along with melee battles, grenade battles, defensive strategy, offensive strategy, vehicular combat, and almost everything else except for aerial combat. It is the most well balanced map out of all the games. You may not agree with all the entries on this list, but Zanzibar needs to be in your top 5 .
Honorable Mentions: Beaver Creek, Sword Base, The Pit, High Ground, Midship, Lockout.