If you're going to make spears and pikes out of music wire, you'll need a dedicated hardened wire cutter. (I suspect the links others have given you will be just fine.) I have one of those, but I no longer see any value in using music wire for spears, pikes, or pins.
Any more I only use mild steel (usually straightened paper clips) or brass. For weapons, I typically use brass. When using a softer wire like these, nearly any diagonal cutter will be just fine, though I would not ever recommend using a sprue cutter for any sort of wire.
Another advantage of brass for weapons is that you can grind on a point, then crush the pointy end of the wire with flat-jawed pliers and get a very passable leaf-shaped blade (especially in 15mm).
HTH