There's a difference between Dollar Tree Stores and 99 Only Stores. If you're lucky enough to have a 99 Only in your area, check them out. DT buys things that they can get full mark-up on and still sell for $1.00. 99 Only Stores has a different philosophy. They try to buy things that generally sell for more than 99 Cents, but for whatever reason the manufacturer wants to get rid of. Subtle, but significant.
At 99 Only, recent purchases include Earthbound Farms Organic Produce, Dole salad greens. Scallions, cilantro, peeled garlic, Mountain High yogurt in 32 oz. tubs. Four packs of Jello Pudding for DH's lunch. I sometimes find Kraft Cracker Barrel Cheese. I always find whole wheat tortillas, 22 packs of Maizada Tostadas, toothpaste, sunscreen, glassware.
Knowing your prices/quantities and shopping there regularly are key to scoring good deals. It is really important to know standard quantities. At Dollar/99 Only type stores foil is typically only 25 feet. Zip-type bags tend to be 8/10/12 packs. Not good on a cost per unit basis.
Also 99 Only Stores charge 99.99 cents per greeting card. Dollar Tree slays them with cards priced at 2/$1.00.
Also for clarification: 99 Only recently increased their prices to 99.99 cents per item. They also sell gallons of milk and pounds of butter at higher prices. They have also begun introducing produce priced by the pound. Fresh grapes for .9999/lb, yes, ma'am!