Ninjago weapon seen in some of the 2012 Spinner sets. It is a dark grey hatchet almost exactly the length of a Spear, similar in form to it's variant, the Dark Axe. It is described as a simple, inexpensive weapon that is perfect for warriors just beginning training. Although implied to be a Ninja weapon, it also appears in the hands of numerous Serpentine as well - notably, Lasha is known to wield a silver variant of the Trusty Axe.
If you're just starting out, and you have limited Ninja experience or budget, the Trusty Axe is the way to go. High quality, low maintenance and cost - you can't go wrong. You'll keep this baby forever.