If you have read (or watched Ender's Game), you're probably familiar with the Battle Room. It's the zero gravity room where two opposing fight with weapons that freeze enemy players in pace when shot. The goal is to either freeze the entire team or get five members of the team in the other teams base.
Someone (who goes by Aurelien-131 on Reddit) managed to recreate the Battle Room in Halo and it's awesome. Of course, there are a couple tweaks; instead of freezing guns, players have Plasma Pistols with infinite ammo and the game can be beat with two players in the enemy base – it would just take a long while (four or more players in the enemy base and it's almost insta-win). You can also win the round by killing the entire enemy team.
One of the hardest aspects to get used to in this map is the fact that there is no gravity. Luckily, the creator had a couple of tips:
Going up is as simple as jumping, but going back down can be tricky. Ground pounding is the obvious choice, but for a slower and more controlled descent you can simply zoom in so that your stabilizers activate, which will make you fall when you let go. As a last resort you can also boost to the nearest wall and the downward slope of the sphere will guide you down.
If this is your jam (and it should be), you can download the map here:
