This seems like a no brainier, but a good
Tool bag to hold your Hammers, marking tools, pencils, markers, plumb bob, hand tools (screw driver, ETC) that you use a lot along with all of those items that seem to walk away on there own.
Added Items:
Carpenters square, 2ea
One foot level along with a three foot one
1-2 chalk line with a refill bottle
Miter Saw Protractor, small one, great for trying to find what cut (angle) you need in that special area.