--> Forgetting to thoroughly clean out the inside of the cockpit before the first session (remember, this is my DD).
Off the top of my head, I've left a radar detector teetering on the passenger visor; had a tennis ball roll out from under my seat and bounce around the pedals (scary as hell); had fast food napkins fluttering out the window down the backstretch at RA (embarrassing but not lethal); numerous metallic items (wrenches?) rattling around in the glove compartment thru the turns; etc...
Sometimes that first morning at a track event can be hurried to get going...
