Tool use was observed for the first time in wild gorillas, as reported by Thomas Breuer, Mireille Ndoundou-Hockemba and Vicki Fishlock in their paper in PLoS Biology. One gorilla broke a branch off and used it to test depth in murky water; another used a broken-off branch to steady itself and then as a bridge over swampy ground.
You can also read about it in the handy synopsis written for the general reader.
This is a big deal, inasmuch as gorillas have been taught tool use in captivity but it hadn't ever been observed in nature. The thought is that they live in such food-rich areas that they don't typically need to resort to tool use to survive.