Custom Sounds
(HEK) Halo Editing Kit for Halo CE
http://hce.halomaps.org/index.cfm?fid=411
Halo Custom Edition Game [English]
http://hce.halomaps.org/index.cfm?fid=410
Tool++
http://hce.halomaps.org/index.cfm?fid=578
Acid Pro 7
http://www.sonycreativesoftware.com/acidpro
Audacity (Free Sound Editing Program)