Linux: Erase/clean MBR(partition table included) of a (pen)drive/block device using dd command

MBR size is (in bytes): 446 + 64 + 2 = 512

446 bytes - Bootstrap code.
64 bytes - Partition table.
2 bytes - Signature.

So
# dd if=/dev/zero of=/dev/sdb bs=512 count=1
cleans everything in the MBR.