Note: I'm about 25 minutes late in submitting to this challenge, but, in my defense, my power went out for about 30 minutes. Anyway, on to the descriptions.
"Mad" Maxine and Jason were best friends, and massive nerds. Jason was into most forms of science-fiction, as well as studying for a Ph. D in biomedical engineering. When the zombie plague hit, he grabbed his LARPing armor, homemade Klingon Bat'let, and homemade Wolverine claws (based on the ACTUAL Wolverine claws recently invented) and gathered supplies along with Maxine in preparation for the apocalypse. After society fell apart, he and Maxine gathered police equipment, including an experimental taser gauntlet (which alo exists, by the way) which Jason wears on his left forearm. He also wears a pack on his back to supply his taser his electricity if necessary, and (more importantly) to hoold the hydraulics necessary for his Wolverine claws to work. Despite being a fairly hefty guy, he's surprisingly agile, and his intellect helps make up for any other physical shortcomings.
Maxine was a horror and zombie movies nerd. As such, she was always planning for a future zombie apocalypse. So, naturally, when it hit, she was prepared for anything!
Except a surprise attack on her right arm. Before the plague should spread throughout the rest of her body, Jason acted upon instinct, and cut off her arm right below the elbow. This freed her of the curse of the undead, but cost her her arm and a small piece of her sanity. Maxine was never very mentally stable, and this event was a major tipping point. Jason, with his engineering knowledge, and expeience with medical technology, outfitted Maxine's arm with a prosthetic arm with myoeletric attachments (which, again, exist in reality), which allow her to control one finger on a prosthetic hand. This finger is holding on to a trigger for a chainsaw held by her prosthetic hand. Like I said, Maxine is a horror nerd. Who wouldn't pass up having a Bruce Campbell chainsaw arm?