Either version works fine: a custom +hard move or plain old Under Fire. Just ask yourself, "if this was a movie, how would I present the zombies? What does it look like when protagonists fight them? Is it cool or is it hard?"

Good point. I'm also thinking about an Apocalypse Zombies game, and am leaning toward using a Dungeon World style "do something under fire" move for dealing with Zombies. That is, the first question is "how do you act under fire in relation to the zombie threat?". If its by powering and pushing through, then roll +hard. If its by keeping your head calm and avoiding their bites, then +cool. 

Once, my dear operator Fox helped her fellow battlebabe read her, as Fox really wanted the battlebabe to understand how hurt she was because of the battlebabe's violent actions and related coldness and detachment. It was a lovely scene.

My take is the following: If there's a battle, the gunlugger counts as a gang and I use the gang rules for dishing out harm (both ways). What weapons are used only informs us what harm the gang causes (e.g. is it a 2-harm or 3-harm gang); in themselves the individual weapons are irrelevant.

If there isn't a battle, then NTBFW doesn't apply.

The "area" tag is then only ever mechanically applied (just like other tags, I think) when you as an individual fires grenades into a gang of sorts.

In response to the OP: it varies. I'm now only playing AW in one group and it's with old friends and we are open and comfortable with each other about everything, including sex.

There is a fair amount of sex in this game, at least involving our dear Gunlugger Barbarossa who has two steady girlfriends and is always looking for more. The player may well be influenced by the positive effects of his sex move. (Another player plays the Driver and despite his general smoothness he keeps it in his pants.) Thing is, we don't go into detail every time Barbarsossa gets intimate with one of his old flings, it's old news so to speak.

One of my favourites scenes in the campaign involved explicit sex. The third player's Angel (Bish) had a visit from Fluffy. Fluffy's one of Barbarossa's girlfriends who came to Bish to get some help as she wants to get pregnant but never manages. Bish starts working on her with healing touch or his infirmary (can't remember) and it becomes apparent that Fluffy's infertility has something or the other to do with the psychic maelstrom. In order to find out what's wrong, and possibly cure her, Bish has to explore Fluffy's sexual nature and we played it all out. It was awesome (and not only because Barbarossa's player's jaw dropped to the floor).