GW has a tool for almost every job but in all honesty, they don't have everything or have the proper design for such things.
1. Revell (Revell Monogram in the US) Contacta glue.
GW sells good plastic glue, only the bottle for application of this is poorly designed and not a great way to carefully apply small amounts of it. Before I got into Warhammer I built a model kit from time to time and for that I used these handy dispensers. Perfect for carefully applying glue to small areas and easy to dose. Only downside to this is that the "needle" can clog very easily when left unattended and not easy to clean, unless you have small rods of 0,02mm around.
2. Tamiya Weathering Master.
To me, there is no better company for model kits than Tamiya, a Japanese company who has been at it since the sixties and has yet to fail. They offer special small weathering kits for use with their model kits, which may look somewhat like mascara boxes, but are in effect great ways of applying weathering and dirt effects.
So, do you people have any handy non-standard GW tools or hobby aids that you use?