Have a paint war. Get large bath sponges and cut them into baseball size sponges then dip them in buckets of washable paint and go crazy.
Make a list of outrageous things on a Bingo card like mullets, scrunchies, spandex pants and hiking boots, etc and walk around WalMart trying to find people sporting the items on your bingo cards. Loser has to buy the winner Hot Pockets for dinner
Eat lunch in the middle of a round-a-bout. Bring a blanket and a basket, have fun, and watch peoples faces as they circle you :)
Play hide-and-seek with multiple couples in WalMart! You and your date are a team against the other couples!
Build a fort in your house using blankets and tables/furniture..etc. Then you can play games, watch a movie, do a coloring book, do a puzzle..anything you want inside the fort.
Find some good skipping rocks, buy some glow sticks, and go to a lake. Take a plastic bag and put the rocks in the bag — break the glow sticks open and pour them into the bag with the rocks — mix it around. by the way you do this at night. Then skip the rocks and see them glowing as they skip across the water.