I've run into quite a few of the new melee variants in missions, but haven't encountered any in the shops yet, so it might be that going for salvage is the best method for acquiring them. I haven't played with the Assassin, but it might have the speed to actually make good use of the claw or hatchet you equip it with. You get an Assassin-25 and the Hatchetman for completing the DLC mission chain. That said, you're probably going to want to just keep an eye out for the new variants, since they get all the flashy new melee weapons. I can't recall if I've seen any small melee weapons. The nomenclature is also confusing, because we have light medium melee weapons, medium medium and medium large, heavy medium and heavy large, and assault medium and assault large options. Join up with the Independent People of Skye to capture the Lyran Commonwealths newest BattleMech, the Hatchetman, in a 5 mission quest line.

There are upgrades for either of those, I'm not sure how their damage and range looks compared to just not equipping anything at all. It looks like all the existing variants had their fists and lower arm weapons converted to medium melee weapon slots. Like Taolan13 said, it's really just trial and error at this point.

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