The Video Game History Foundation uploaded an archive of E3 2000 show floor footage last week. It's quite the time capsule. The cleverly deceptive MGS2 trailer is in it! Also many things "best left in 2000".
Halo.
The e3 2000 trailer was when it was under development as a PC title, prior to the buy out of Bungie by Microsoft, after which (?) it became an xbox exclusive.
Halo was released to Xbox in 2001 and by 2003 both a MacOS and Windows port were released. "Delayed" maybe, but definitely not "never released".
I played quite a bit of Halo on PC in high school with my friends, sneaking into a nearby university computer lab and usurping it as a LAN party room. For some reason those Windows machines all had Halo pre-installed on them.