If you compile the kernel with FireWall support then you could
ipfwadm -I -P icmp -a reject(or deny)
that would make it so your computer wouldn't reply to the pings from any host.
But lets say that you wanted to be able to be pinged by brigia.blitz.com but not by anyone else well then you would
ipfwadm -I -P icmp -a accept -S brigia.blitz.com ipfwadm -I -P icmp -a reject(or deny)
make sure you put the accepts first then the deny's or rejects.
Hope this wasn't too confusing,