When I was in Boy Scouts I learned a great many skills that I still posses today. Two that I spent considerable time in practice and have since forgotten are tying knots and CPR. While tying knots certainly has its place and I would like to return to learning at some point, CPR could at some point become a critical skill.
CPR is wroth getting retrained especially since they have change the technique. According to the American Heart Association 300,000 sudden cardiac arrests happen annually outside the hospital setting alone. Only 37% of these victims get CPR. However, administering CPR can double or even triple the chance of survival.
I hope I never have to use CPR but I would rather be able to attempt to save a life than watch helplessly waiting for paramedics should the situation arise.