If you're the only person on the system, you can use now instead of an argument in minutes. For example, to reboot the system right now:

# shutdown -r now

No chance to hit control-c in this case; the system is already on its way down. Finally, the -h option halts the system:

# shutdown -h 1
Broadcast message from root (pts/2) (Tue Jan 15 19:50:58 2002):
The system is going DOWN for system halt in 1 minute!