So far you have received great tips.
Do not know if you have gone ... but here is what I am taking to mine tomorrow. The usual list - sewing machine, lamp, Extension chords (2 - one that is three prong / grounded and one that is not - I have been in situations where there is not an outlet that is grounded), small ironing surface and small iron. I also bring a medium size cutting surface, rotary cutter, replacement blades, a long narrow ruler, a 6x12 ruler, I do not usually purchase specialty rulers but if you have one and use it for your project - then do not forget it, replacement needles, pincushion, pins and thread catcher, marking pencils or chalk, a few snacks, several plastic bins that hold single projects - more than I plan on working on as I too have messed up a project or not had what I needed to complete a project - I want to keep busy, and a small folding hand dolly with a couple of bunge cords.
I too mark everything with my name. I use those "free return labels" we all get at the holiday seasons on rulers mats and big stuff. Works great for me. I also mark all my scissors with a cell phone charm loop on which I have added a charm/ bead. Scissors and cutters all look alike and when someone "borrows" mine I can always identify it.
One last I always bring is a tall plastic container(I use a Crystal Light Package with the little snap on lid) - large enough to hold my scissors, rotary cutter and seam ripper point down at my station.
One last note - get in the habit of using something then putting it away when you have finished with it. Things walk easily at a retreat because everyone's scissors, cutters, rippers and rulers look the same sitting side by side.