This particular shovel is probably not my first choice of weapon. It's a bit too handle heavy and short so not a good club. It'd take some training to reliably strike with the blade with good edge alignment. It handles like a short baton or short pipe with an annoying blade on the end. The length is also not short enough to be manoeuvrable but not long enough to give much reach. It'd be much better than nothing but I just didn't feel right when I tried it as a weapon. It does look mean though.
I can wield this one-handed, and it feels okay to use this in my off hand with a knife in my dominant hand. In that mode, this spade is more for stand-off, defense and distraction while the knife does any dark deeds. That's fair because if I have the spade I'd probably also have a knife.
If I was cracking zombie skulls then I'd probably go with the spade in the dominant hand. The spade's lightness upfront means I'd want maximum power and dexterity to get that coconut cracking edge alignment. Probably a 6/10 in the weapon stakes just because it feels weird.