WinGate This piece of software allows multiple people in an office to share a dialup line and has some rudimentary firewall capability.
X Watch Window If you have access permission to a host's X server, XWatchWin will connect via a network socket and display the window on your X server.
xcrowbar.c Source code demonstrates how to get a pointer to an X Display Screen, allowing access to a display even after "xhost -" has disabled acess. Note that access must be present to read the pointer in the first place! (Originally posted to USENET's comp.unix.security.)
xkey.c Attach to any X server you have perms to and watch the user's keyboard.
YPX YP/NIS is a horrible example of "security through obscurity." YPX attempts to guess NIS domain names, which is all that's needed to extract passwd maps from the NIS server. If you already know the domain name, ypx will extract the maps directly, without configuring a host to live in the target NIS domain. (GZip'd Bourne Shell Archive)
