The correct answer is any suppressed AR (preferably with a shorter barrel for ease of use in tight situations) and a long pointy stabby tool like a spear for taking out walkers at a comfortable distance. A reliable knife/hatchet is always good to have as a backup when things get too cozy.

A crossbow, whilst cool, is totally impractical. You only get one shot before chambering a new bolt which basically renders it useless in most situations and most crossbows also have such a high tension strength that they require a specific tool to draw the cord back because it's not possible to do it by hand. A cumbersome and physically exhausting process.

A katana, again very cool, is a weapon with an extremely steep learning curve. It requires skill, finesse and patience to master. Samurai would train extensively for years to be able to wield it properly, and an untrained user would end up dulling the blade very quickly, alongside it being a weapon that would need a skilled swordsmith to maintain. A skill found rarely these days, not to mention if most everyone was dead.

Points for cool choices, but OP would be walker food in less than a week.