BusyBox

BusyBox is a single binary that provides several stripped-down Unix tools in a single executable. It runs in a variety of POSIX environments such as Linux, Android, FreeBSD and others. It was specifically created for embedded operating systems with very limited resources. It has been self-dubbed "The Swiss Army Knife of Embedded Linux". It includes clones of netcat, httpd, init, grep, a dhcp client/server, tar, sh, ash, awk, cat, and many more utilities.