Okay, here's a couple I use:
Junior Jigsaw/Coping Saw Blade in an X-acto knife holder
I got this one from a Punished Props video. the X-acto holds on to a blade surprisingly well, and with a little patience, it can go through aluminium, no problem. it works like a miniature jab/keyhole saw. I normally have thin coping saw blades in there, which makes it great for inserting into drill holes and cutting into those hard to reach places.
Miniature chisels made from sharpened Jeweller's screwdrivers
Not so much a metalwork tool, but I've ended up using these somehow on every build of mine. really useful for shaping 3D printed parts- especially Shapeways prints. I've also used them as improvised turning tools for my attempts at turning things on my drill press, to great success.
Got to give a shout out to Milliput epoxy putties. great stuff for filling him holes that shouldn't be there, and it's water sculptable. I know old modellers who swear by the stuff. the only downside is that I understand that it's one of those products that hasn't made it Stateside, so it might be hard to get cheaply outside the UK.
I also use high-grit scotch brite-type pads. I can't remember the proper brand name, but I get it at a wood shop in the polishing section. I use it for finishing instead of wet sandpaper, or before anodising. It gives as a good a result as sandpaper, and can be cleaned out, dried and re-used, unlike sandpaper.