Andrew McKaige
From Halopedia, the Halo wiki
Australian actor Andrew McKaige was born 1959 in Melbourne, Australia. He has many Australian acting credits to his name including dramas, such as The Secret Life of Us and All Saints, and soap operas, such as Sons and Daughters, Neighbors, and Paradise Beach.
In the Halo video game series he voices the Marine Chips Dubbo in Halo 1 and Halo 2.
Bungie uploaded some outakes from their voice over sessions and you can listen to some Dubbo bloopers:
