Grrr. Smit[1]. A non-optional (in many cases) tool to accomplish administrative tasks on AIX boxes. Making it nigh impossible to script common stuff that was easy on any other unixish OS.
It is a shame. Many challenges we find today happen to have been solved in the 60s. Then in the 70s, then in the 80s...
EDIT: One thing that I love is the fact that they distributed apps in intermediate form and then compiled at installation time. (Sounds familiar, right?)