COMMON LAW: The Depo Kit
Post-it notes. For marking documentary exhibits, mainly. Also for noting when you need to get the spelling of names to keep your court reporter happy. There are going to be enough paper clips there to keep multi-page exhibits together should opposing counsel be so inconsiderate as to produce them without staples.
Highlighter pen. For marking down important things you notice on exhibits for the first time, or for marking down things you determine opposing counsel thinks are important on those exhibits.Food, in convenient compact bar form. Maybe for yourself but more likely for your client. Keep her blood sugar high, so she can concentrate on the task at hand and not become any more irritable and stressed (and therefore uncharismatic) than need be.