Netcat

Remote Shell

$ nc -l -p [port] -e /bin/sh

If -e flag is missing (OSX):

$ nc -l [iport] | /bin/sh | nc -l [oport]

File Transfer

Host file on port.

$ while true; do nc -l [port] < [file]; done;
Download file from host.

$ nc -w3 [hostname] [port]

Port Scanning

nc -z [hostaddr] [ports]

$ nc -z 127.0.0.1 1-1024