These are the top ten maps in the Halo series in my opnion. Now you should know my Halo expereince really took off with Halo: Reach but I have played many of the great classic Halo maps from the original trilogy in the MCC, forge remakes anf the actual games themselves. Enjoy!
Honorable mentions: Guardian - Halo 3, Sanctuary - Halo 2, The Pit - Halo 3, Midship - Halo 2, The Spire - Halo: Reach, Exile - Halo 4
10. Zanzibar, Halo 2
Many would rank this map higher and rightfully so (there are just 9 more maps i like better). This is one of the most unique maps in Halo's history as it is a landmark map for Halo 2 and 3. This map offers intense action from it's open areas, the beach, the platfrom next to the wheel, to the small corridors in the structure behind the wheel (not the most avid description I know) and of course the wheel itself provides memoralble, fun combat and the variety of vehicles just adds to the mayhem.
9. Epitaph, Halo 3
One of the most slick and gorgeous maps in Halo. Epitaph is one of my favoirte close quarters, small team maps with players never knowing whats around each corner or if they'll get hit out of nowhere by the rocker launcher. Free for all is the most fun to me as the entire map is in constant action. Just make sure you keep an eye on your surroundings or you might take a tumble over the edge.
8. Haven, Halo 4 
Haven is for sure my favorite small map in Halo 4. It's beautiful design adds to it's unique fell and the narraow corridors have some of the most fast paced action. Teamwork is key on this map as am "every man for himself" approach will lead most any game mode to essentially a free for all which works great too. For the large fan base Haven was a huge stand out map for Halo 4.
7. Snowbound, Halo 3 
The vast, open area of Snowbound created excellent long range battles for any weapon and the caves underground were crowded with bullets and explosions. Usually whoever controlled the ghost controlled the map unless the turrets got em. There's only one other snow map in the Halo series better than this one.
6. Complex, Halo 4 
The oddball (get it?) pick in this list. Complex isn't on a whole lot of best Halo maps lists but I don't care beacaue I love this map to pieces. The size is just right for near any game mode and the buildings all have their own specific feel. This might just be my favorite map for SWAT and one of my favorites for Infection along with Big Team Battle and King of the Hill. Complex was my personal favorite map in Halo 4 not Ragnarok as that map is a remake of another map I'll get to later.
5. Ascension, Halo 2
There has been multiple popular forge remakes of this map for a reason. Ascension is fun, intense, one of a kind and a true classic in the series. From the sniper rifel to the Banshee this map has no short of variety that has kept players entertained for years and will live on for the years to come.
4. Hang'em High, Halo: Combat Evolved
One of the best and for sure most unique map designs in the series. The pillars, the trench, the bridges, the ramps, all of it just adds to this brilliant map. The whole thing really is just a huge mess of variuos structures but it works masterfully for 1 v 1 matches to big team battle mode.
3. Battle Creek, Halo: Combat Evolved 
The quintessential map for small team vs. team gameplay. You can have a tight fight in the creek, get sniped from the high rocks or run into the enemy team in your own base. Some of the fastest paced action is found on Battle Creek and it delivers the most intense Capture the Flag games and the simplicity of this map is one of it's best features. Also everytime I play on this map I think of the hillarious Red vs. Blue bit when Caboose and Sarge are trapped on this map with two teams of crazed reds and blues forever destined to fight eachother.
2. Lockout, Halo 2 
Now this is best map in the Halo series with snow on it (not as much snow as Snowbound I know but whatever). Lockout is without question the best small map in Halo as players never knew what was around each corner but if you managed to get the energy sword then you would feel pretty confident. Lockout is smart and endlessly enjoyabe from the standar Slayer modes to Oddball, Lockput will always have a huge place in the heart of Halo multiplayer.
1. Blood Gulch, Halo: Combat Evolved 
The obvious pick for number 1 and rightfully so. This bloody gulch is legendary and played a massive part in making the multiplayer become as huge as it is. The two bases in the vast canyon have made an untouchable mark in the series; it gave us Red vs. Blue, it gave us the best big map in the history of FPS multiplayer, it gave us excellent forge remakes, it gave us Valhalla and Ragnarok and it's greatness in undying. Thanks for everything Bloof Gulch we all love ya.
What are some of your favorite Halo maps?