Here you go:

(they are not listed in alphabetical order. this will be updated daily!)
speak "officer (name) report to Sector D for immeidate questioning"
speak "bizwarn bizwarn attention military !delay=0.7 officer at sector [letter]"
speak vox_login
speak "this is a test of the Announcement system" - Tests only
speak "error" - ?
speak "bizwarn bizwarn biohazard at sector [letter]"
speak "[name] wanted for questioning"
speak "[name] report to sector [letter] for questioning"
speak "bizwarn this is a test of the Biohazard Warning System. bizwarn"
speak "bizwarn bizwarn bizwarn radiation overload at sector [letter]"
speak "error warning _period system !delay=1 override"
[MILITARY OVERRIDE] speak " THIS IS A MILITARY OVERRIDE ANNOUNCEMENT Military Override"
[MILITARY OVERRIDE] speak " THIS IS A MILITARY OVERRIDE ANNOUNCEMENT The military has taken the announcement system."
[MILITARY OVERRIDE] speak " THIS IS A MILITARY OVERRIDE ANNOUNCEMENT All crew report to surface for questioning"
speak "Military override shut down."
speak "bizwarn radioactive activity detected at sector [letter] bizwarn"
speak "remaining crew to sector [letter]"
speak "the Black Mesa Research Facility is now in full lock down. Stay put."
speak "illegal research detected in sector [letter] !delay=0.5 security officer to sector [letter] to question all research crew"
speak "buzwarn bizwarn buzwarn personnel in sector [letter] go to sector [letter] for questioning"
speak "bizwarn bizwarn buzwarn personnel in sector [letter] go to surface for questioning"
speak "bizwarn buzwarn buzwarn personnel on surface go to sector [letter] for questioning"
speak "buzwarn buzwarn buzwarn all personnel to sector [letter] for questioning"
speak "bizwarn bizwarn bizwarn all remaining personnel to sector [letter] for questioning"
speak "buzwarn security personnel to sector [letter]"
speak "buzwarn security personnel to sector [letter] for daily inspection"
speak "buzwarn security personnel to sector [letter] for inspection"
speak "buzwarn security personnel to sector [letter] for research check up"
speak "buzwarn bizwarn maintenance crew to sector [letter] for repairs"
speak "bizwarn buzwarn cleanup crew to sector [letter] for cleanup"