In reply to JohnO1978:
I've not used a macebell but have used clubbells which are similar, for a long time. Scott Sonnon is a very good authority on them and a good source of info on exercises and technique. Most of the time I use the overly excitingly named "trial by fire" with 6kg clubs as a warm up before other weight training. It consists of the following:
100 Double Swipe
100/100 1H Mill
50/50 2H Hammer Swing
Takes about 14 minutes now.
Good for functional fitness, particularly shoulder mobility and some grip strength. I think fingerboarding has been more impactful for climbing directly for me. But I still use them most days for something. The off balance nature of the weighting is great for stabilizer muscles.