Really quick for loop I just ran for a bunch of files in a directory that I wanted to no longer have a .pdf extension:

for file in *; do ext=${file##*.}; fname=`basename $file .$ext`; mv $file $fname; done

Inspiration from here.

Mario Loria is a builder of diverse infrastructure with modern workloads on both bare-metal and cloud platforms. He's traversed roles in system administration, network engineering, and DevOps. You can learn more about him here.