Infinite Marines glitch

On the level The Storm after defeating the Scarab and going through the aid station you will come across several Marines fighting some Brutes in a large storage room. Defeat them and go into the next room and you will find several Voi Factory Workers fighting the Brutes. When you enter this room let all the marines and workers get killed, after their all dead, 2 marines will spawn in the previous storage room and join you. If they die then 2 more spawn and so on. For some entertainment you can lead the Hunters in the next area back to this storage room and watch them destroy countless Marines or you can start killing them. The glitch can be useful on Legendary because infinite marines will eventually kill off the brutes and hunters. They stop spawning when you go out outside.

Infinite marines can also be found on The Covenant. When you get the Hornet and are flying to the third tower you will see an island with an AA Wraith on it. Destroy the Wraith, land on the island, and drop your Hornet into the water. Another Hornet will come and land, then drop it into the water and another will show up. Each Hornet carries 1 marine and will keep spawning, although the map will overload eventually.