Every now and then I connect to a server and need to install something. But since nobody tells me which distribution is used, I have to find out myself. uname -a mostly does not give a hint, especially on self-compiled kernels. Trying each known package manager binary (yum, emerge, apt-get, ...) gets tedious and you still don't know which version you really are on.
cat /etc/*-release Gentoo Base System release 126.96.36.199
cat /etc/*-release CentOS release 5.2 (Final)