Terro liquid ant killer - 2-ounce bottle
This is the 2-ounce bottle. It's also sold in a smaller 1-ounce size. Price varies pretty widely so it's a good idea to shop around. The 2-ounce size is available at Lowes for $3.97. Ace Hardware carries the 1-ounce bottle for the same price so it definitely pays to look around a little bit.
Complete ant control may take up to 2 weeks. Or so they claim.