I have tried pretty much everything that you mention... flat, extremely thin "rolls" of duct tape, flat meds packaging etc. I have yet to find something I am really happy with and my kit is still currently much larger than I would prefer. As far as containers, here are the ones that I have tried that I can remember (I'm sure I'm leaving out a few.

Standard Altoids Tin
Round Altoids Tin
Mini Altoids Tin
Round Candle Tin
AMK Pouch
FAK Nylon Pouch
Small Plastic Boxes (in a variety of shapes and sizes from SparkLite to FAK)
Empty Zippo Lighter Shell
Dental Floss Box
Spark Lite Box
Spec Ops T.H.E. Wallet Junior
Regular (very small) Eagle Creek Wallet
Key Ring
Caribiner
My Pockets
Taped around a knife sheath (much like a large version of Cody Lundin's mini kit)
Maxpedition M-2 Waistpack (many smaller kits have been put in the M-2 along with a Storm Shelter Instant Pocket Tent)