~ My beloved hobby knife by X-acto with #11 blade is THE tool of the trade. The hobby knife is for the modeller what the scalpel is for the surgeon! I put on a new blade every time I start a new build.
~ Sanding sticks, from coarse to extra fine, tapered. Squadron is my favourite brand.
~ A couple of sprue cutters.
~ Tamiya masking tape
~ Glue, of course. My favourite is the Contacta by Revell
~ Putty (as for the sanding sticks, by Squadron mostly). Putty is great. Not only you can use it to fill gaps and seams (you’ll use putty quite a lot), but also to simulate zimmerit paste and to craft tarpaulins, rolled blankets and similar objects made of some kind of fabric.
~ Pin vice. You’ll want to start drilling stuff eventually 😀
~ Tweezers of every shape and size
~ Soldering kit for photo-etch
I also have countless other tools but the ones I just mentioned cover 95% of my needs during the building stage.
Resources for scale modellers 