If a USB flash drive is present, have the system automatically mount it and then execute a pre-determined named script. This would allow something to the effect of an rc.local file (for those Redhat users) that can be edited on the USB disk and then run at startup.

This would be useful for:
mounting network shares automatically
executing customized scripts (e.g. for imaging a system with partimage)
to automate installing knoppix on the hard drive
... the list could go on and on.

A feature of this nature would give the Knoppix community a lot more leverage in the usefullness of this bootable CD.