AP also does some investigative work. For example, "Americans buying salmon for dinner at Walmart or ALDI may inadvertently have subsidized the North Korean government as it builds its nuclear weapons program, an AP investigation has found" https://www.apnews.com/8b493b7df6e147e98d19f3abb5ca090a
That said, Reuters does do solid investigative journalism work. One example is the Taser scandal recently: https://gijn.org/2017/10/02/how-they-did-it-reuters-massive-... They also have opinion pieces, and long form pieces, although these aren't seen as much as their standard articles.