The Special Purpose Sniper is a deleted Covenant species seen in the Halo 2 Collector's Edition DVD. Its arms were used like a tripod (but not act like one), and that it could flip from side to side, without having to switch weapons. It would also be able to hang from trees and building struts. It could have been used instead of the Jackal Snipers in Halo 2.
While developing the Halo games, Bungie, 343 Industries and Ensemble Studios have had to cut some content, such as vehicles, gameplay, and story elements, from the final products. Much of this content has been confirmed by videos and commentary in special edition DVDs, interviews with developers, and released concept art.