ident-user-enum is a simple PERL script to query the ident service (113/TCP) in order to determine the owner of the process listening on each TCP port of a target system.

This can help to prioritise target service during a pentest (you might want to attack services running as root first).  Alternatively, the list of usernames gathered can be used for password guessing attacks on other network services.

Unix-privesc-checker is a script that runs on Unix systems (tested on Solaris 9, HPUX 11, Various Linuxes, FreeBSD 6.2).  It tries to find misconfigurations that could allow local unprivilged users to escalate privileges to other users or to access local apps (e.g. databases).  

It is written as a single shell script so it can be easily uploaded and run (as opposed to un-tarred, compiled and installed).  It can run either as a normal user or as root (obviously it does a better job when running as root because it can read more files).