I'm a real estate investor with 25 properties, and we've used Keller Williams for our last 4 investments, and plan to continue to use them. They've been amazing.
Two agents to point out in particular - Cynthia Dillingham and Ryan Dodson.
Both specialize in investments - Cynthia does a lot of Forclosure listings, Ryan (yes, we're related) does both Forclosures, Rental Property, and "signfigantly undervalued" property.
Everyone at Keller Williams works hard for their customers. I don't have anyone to recomend for buying a personal home, but if you're looking for investments, Keller Williams is the way to go.