A three-piece suit gets noticed. It's a bit daring, without actually being risky. You're making a strong visual statement, but in a deep blue or a lightweight gray flannel, you're still playing it fairly safe. And you don't have to wear the vest if you don't want to.
It's also a nice option if you take off your coat at work. You still maintain a sense of formality in shirtsleeves. Haven't worn a three-piece suit in a while? Or ever? You'll be surprised at how good you look. Just remember not to button the bottom button on the vest and you're in the clear.