I'll edit this as the ideas flow:
1. a GUI for helper/admin commands (refer to Saurebraten)
2. Instant Replays for Spectator Mode under certain circumstances like;
Rockets going off in non-rocket modes
Successful grenade throws from over 50m
Headshots over a certain distance 'x'm
Kill streaks
etc.
3. /tell /whisper /msg or other variant :P
/tell {cn} "Message"