Bash allows you to save some typing by referencing the previous command's parameters via a variable. If you want to reference the first parameter from the previous command you would use !^ and if you want the last parameter you would use !$. A real world example would be something like this:

mkdir /long/dir/structure/new_dir
cd !$

This would make a new directory and then change to that directory. Alternately you can reference numbered parameters using !:2 to reference the 2nd parameter.