trap true TERM
kill -- -$$

The first line means that when the shell receives a TERM signal, it executes true. The normal behaviour would be to kill the process, so this means that the shell is immune to people sending a TERM signal to it. The second line sends a TERM signal to the process group (- is the modifier to indicate a the process group of the PID, not just the PID) of the current process ($$).

The end result? Everything spawned by this script which hasn't gone and re-parented itself is killed: the ultimate in cleanup.

NP: Dedications, Klimek