As reported by xlr8yourmac.com, a downloadable demo of Activision's Return to Castle Wolfenstein is due out today, Saturday the 15th. It had been assumed that this would be a PC-only release, but a quote from Graeme Devine's .plan file might indicate otherwise:
" Mac stuff.
I've been playing the WolfMP test natively under Mac OS X. I've also got the OS X installer for WolfMP all wrapped up and standing by. "
Recall that the Quake III Arena demo came out for the Mac (OS 8.x) a couple of weeks before any other versions surfaced. Download links, etc. avail at the main game page (above link)--keep an eye out for it sometime today.