If you want to do it with a script or with the CLI, remember that the disk cannot be mounted or otherwise be in use. If you have a few disks to wipe, it will save time in the long run if you use a script like the one shown below. This script wipes the first and last 4096 kilobytes of data from a drive ensuring that any partitioning or MetaData is gone and you can then reuse your drive. Warning, all other data on the drive will become inaccessible!:

#!/bin/sh
echo "What disk do you want"
echo "to wipe? For example - ada1 :"
read disk
echo "OK, in 10 seconds I will destroy all data on $disk!"
echo "Press CTRL+C to abort!"
sleep 10
diskinfo ${disk} | while read disk sectorsize size sectors other
do
        # Delete MBR, GPT Primary, ZFS(L0L1)/other partition table.
        /bin/dd if=/dev/zero of=/dev/${disk} bs=${sectorsize} count=8192
        # Delete GEOM metadata, GPT Secondary(L2L3).
        /bin/dd if=/dev/zero of=/dev/${disk} bs=${sectorsize} oseek=`expr $sectors - 8192` count=8192
done