Bulk rename/move files

gistfile1.txt

Simple reminder for myself next time I've downloaded a bunch of files with the wrong, or no extension...

Given the following wav files in a dir:
50-13-0
50-13-1
50-13-2	
50-13-3	
50-13-4	
50-13-5	
50-13-6	

Running: ls | grep "50-13" | xargs -I '{}' mv '{}' '{}'.wav

Results in:
50-13-0.wav
50-13-1.wav
50-13-2.wav
50-13-3.wav
50-13-4.wav
50-13-5.wav
50-13-6.wav