ctrl-r in bash tops my list, even if it's not quite what you are thinking of as a unix tool. Probably the pipe itself would be my favorite next. Then in no pa

ctrl-r in bash tops my list, even if it's not quite what you are thinking of as a unix tool. Probably the pipe itself would be my favorite next. Then in no particular order: tail, cut, xargs, wc, tr, grep, sort, uniq.