Mahoro's primary external firearm is a pistol. Aside from being rather large, it's pretty unremarkable looking - although the punch it packs is more than enough to compensate for it's lack of glamour. In probably the worst design decision in firearm history, they made the pistol belt fed from the top - which defies any common sense in the way you would design it, but it seems to work fine in anime. Also note that Mahoro always grips the trigger wrong, yet could probably still shoot the nads off of a misquito. Although very powerful, the pistol isn't strong enough in itself to win battles against stronger opponents.
Slash is Mahoro's primary support mecha. He looks like a large black cat, although he's all steel underneath. Slash doesn't seem to have any special or hidden talents, but instead attacks the way a large cat would. Slash is also quite intelligent, although not as smart as Mahoro, and while powerful; is not as strong as Mororo either. Still slash plays an important role in taking some of the heat off of Mahoro, and is certainly helpful in having a second opinion if nothing else. Although explaining why you have this large puma looking creature wandering around in your back yard gets to be a pain at times.
Not much to say about Sylpheed. It's basically some attachment to Mahoro that allows her to fly - like a jetpack. It also comes in handy on its own by flying in munitions and support. One puzzling aspect about Sylpheed is how Mahoro can use a jet pack with a full maid outfit and not look the least bit phased. Lots of starch apparently
Mahoro's main weapon is also her most powerful - which I don't recall having a specific name (or maybe it's so secret that no one can talk about it?). The weapon is a sort of energy whip which essentially tears things to peices. It can't be used immidiatly, and requires some set up time to work - usually Mahoro simply grasps her wrist as her had charges before becomming th whip. It is the one weapon that cannot be removed as it is linked to the core of her body, and each time she uses it - her life grows shorter. By the time Mahoro comes to live with Suguru, even using it once would be fatal.
When any ammount of large scale explosives, lasers, and thermonuclear weapons just won't do, an anti-matter cannon is just what the doctor ordered. This has to be one of the least practical weapons in the series. First it takes like half of the power in Japan - note that Mahoro just TAKES it, at least in Evangelion they asked for it! It takes forever to get a shot off. It's pretty much impossible to carry, although it seems to have handles and a trigger suggesting someone carry it. Of course it doesn't really make sense to have an uber combat android lug the thing around just to pull the trigger... eh. Well anyway this thing is pretty much garanteed to put a hole just about anything