I have a few things other that the obvious described above:
These tools are mainly from art and craft shops.
Pallet knives on the left. The Boldmere ones are a cheap set, cost about £3 to £4.
The next two are by Liquitex (if I remember rightly, the names rubbed off with use) and cost £8 to £9 each!
I've had them for a good 10 years and unlike the cheap ones don't need gluing back together every now and then.
Have many uses, painting gluing, sculpting etc...
Cheap toothbrush on the right from a pound shop (from a pack of 4!) useful for cleaning residues off of kit parts for example.
Brass cleaning pen, good for stubborn dirt on loco wheels, brass kits etc...
Top left, cheap sponge brushes. Use for glue, paint, clay etc...
Then we have a set of silicon sculpting brushes. They were cheap, a couple of quid and are very useful in any clay work like waves.
Then an assortment of cheap clamps out of the pound shop.
Compass cutter on the left. Cheap one as its not something thats used a lot but is useful!
On the right we have several perforating tools. These are by Pergamano and are used in parchment craft for making nice shaped holes.
I use them for scribing into clay and plaster. Cost about £8 to £10 each but they last years and can be resharpened with a file when blunt.
The little scissors are for card making/decoupage, cost about a fiver and are extremely useful!
Last of all I have two small pin vices, a normal one and a swivel one. They take up to 1mm diameter bits and are very useful especially when laying N gauge track.