For laptops, I securely place my business card on the lid so that in the event that two identical laptops go through the X-Ray. I heard of a story of two laptops being picked up by the wrong passengers, only for them to be luckily be seated next to each other on the same flight and discover their mistake then.
For my carry-on bag, I have replaced the (worn) wheels with in-line skate wheels of a contrasting color of the bag, and that has come in handy in trying to describe/identify the bag.
