Mentioned in a post, but failing to nominate: Dan Gurney
4 F1 wins
7 IndyCar wins
Never won at Monte Carlo or Indy to be in the Triple Crown winners list, but helped give A.J. his Le Mans title.
5 NASCAR wins (albeit all at Riverside).
Won in the original Can-Am series
And a single win in Trans-Am and it's British Touring Car cousin.
First of two (other being previously mentioned Mario Andretti), to win in the major racing series of the era. F1, IndyCar, NASCAR, SportsCars.
Another vote from me for Daniel Sexton Gurney.
In 1967 Dan Gurney took part in Nascar in the USA, USAC (IndyCar) in the USA, F1 in South Africa, Monaco, Holland, Belgium, France, UK. Germany, Canada, Italy, USA and Mexico, the Le Mans 24 hour race in France, and Trans-Am in the USA. During that year he won 1 USAC race, two F1 races, the Le Mans 24 hour race and 1 Trans-Am race. I'd say that was pretty versatile.
Look a few years earlier and later and you can add drag racing, Bonneville salt racing and winning the first "Cannonball Run" in a Ferrari Daytona (downtown Manhattan to Redondo Beach, California in 35 hours 54 minutes) to his accomplishments.
Or if DSG is too obvious, how about Danny Ongais? a three-time AA Dragster Champion and raced in CART, IRL, F1, sportscars and on motorbikes.