Traveling in the tropics or where you might encounter bugs? Use short bungee cords to wrap around your pant cuffs to keep bugs from going up your pant legs. This also works for long sleeved shirts.
Do you travel with a flat iron for your hair? Did you know they can be useful for getting out wrinkles in your clothes, too? Do check the TSA website as I don't believe they can be in your carry-on luggage.
Not sure you can remember what your rental car looks like when it "looks-like-every-other rental car" in the parking ramp? Take a photo with your digital camera. No camera? Pack a magnet and place it on a door or the trunk.