'State of Affairs' Star -- Katherine Heigl's a Great Kisser ... Just Ask Her Husband

Katherine Heigl is a great kisser ... is probably something Chris McKenna shouldn't say, because she's married!

Katherine's "State of Affairs" co-star jumped at our question with excitement and you can see the lightbulb go off when Chris remembers she's married.

So, Chris gives a shout out to Katherine's hubby Josh Kelley.

Chris was leaving The D Casino Hotel in Vegas, where he had just hosted a Date-A-Thon with 500 horny single chicks all over him.