The list can be quite extensive, or relatively short, depending on cost and desire. Tools, for me, has practically become a hobby into itself.

Here's a start.

a couple of hobby knives with lots of #11s
a razor saw and miter.
Several sanding bars like the ones from great planes.
A good flexible steel rool, at least 18"
A Ell square.
an 18" clear flexible rule.
Dremel with cuttoff wheels and an assortment of carbide and/or diamond bits.
Clamps, clamps, and more clamps. I use the mini quickgrip, mini springclamps and metal binder paper clips.
Wax paper
5 min and 30 min epoxy. If you plan on glassing your plane, you could add West systems epoxy too.
An ultra fineline sharpie and a mechanical pencil.
Painters tape.
Drill
Bench disk/belt sander (optional but usefull)
Drill press (optional but usefull)
needle nose pliers
small flat and philips drivers
tweesers
Mini needle files/diamond files


I'm sure I'm leaving much out such as covering tools if you go the covering route, painting tools if you paint, hinging tools and so forth.

Scott