Great tips everyone! 
Stuff that never gets unpacked from my suitcase, since I travel for work frequently: Night lights (2 small round led ones with the turnable shield, since you never know which way the plugs are pointing in a room), scissors, binder clips, clothes pins, flashlight, travel-sized manicure set, lint roller, travel Lysol spray, travel Febreeze, travel Static Guard, small power strip, moleskin, small first aid kit, and a cell phone charger (my Nook and cellphone use the same type, so one stays at home and one in the suitcase!), every size of Ziploc bags, and plastic grocery bags.
But a couple of things I haven't seen mentioned:
I never travel without Monistat Soothing Care Chafing Relief Powder-Gel. Sometimes hard to find, but have had good luck finding it at Target. (It's stocked in the women's hygiene area near the Midol.) Both DH and I apply it at the start of the day, and again after our midday break. Use it anywhere you might chafe, like your upper thighs, and under my breasts. It goes on like a gel, but turns into a powder. Truly remarkable stuff!
Another must have is Gold Bond Pain Relieving Foot Cream. Quite a few of the drugstores in my area carry it. After a long day at the parks, nothing beats this! In the morning, your feet feel like doing another 10 miles, no problem!

It's mentholated, so fair warning, it can be stinky, so I pack an older pair of socks to put on after the cream, and use them only for this purpose. When I pack for the trip home, I make sure to put these socks in their own special Ziploc so not to smell up the entire suitcase!