The dd command copies a file, converting the format of the data in the process, according to the operands specified.

# To make a bootable usb drive from an isohybrid file (such like archlinux-xxx.iso):
dd if=file.iso of=/dev/usb_drive

# To clone a drive to another drive with 4MB block and ignore error:
dd if=/dev/source_drive of=/dev/dest_drive bs=4M conv=noerror

# To generating a file of 100 random bytes by using kernel random driver:
dd if=/dev/urandom of=random_file bs=100 count=1

# To benchmark the write performance of a disk:
dd if=/dev/zero of=file_1GB bs=1024 count=1000000