Killtacular Pack
From Halopedia, the Halo wiki
Killtacular Pack is a downloadable content package for Halo 2 that was released on April 24, 2005 for $4.99 and was made permanately free on June 28, 2005.
Killtacular Pack added the following content to Halo 2:
Killtacular Pack takes up 99 MB on the Xbox 360's HDD.