I doubt this is the best method, but it does work.
Code:
 alias slapall {
  set %tslap 1
  set %nslap $nick($chan,0)
  while (%tslap <= %nslap) {
    set %slapall  %slapall $nick($chan,%tslap) $+ ,
    inc %tslap
  }
  describe $chan slaps %slapall around with a slapall stick.
  unset %slapall
  unset %tslap
  unset %nslap
}

the usage is just /slapall in the channel. I'm sure someone will come up with something more efficient. My mind just isn't running fully.