Spent 5 mins in line beside Stephen Colbert at a Starbucks in Mount Pleasant, SC on a Saturday morning. I had to go into work and he was up early to work on his boat. Like an idiot I went in to shake his hand after getting up the nerve to introduce myself as a big fan, he had a cast at the time (which was part of his schtick on the show) and gave me a fist bump instead. Couldn't have been a nicer guy. I worked for the state government, so we riffed on that for a min or two. I wouldn't have pulled the trigger and said anything if I didn't see the NJ license he pulled out with his credit card (back when places would ask you do that).
I also saw Timmy D in the arcade of the Pizza Hut on Reynolda (I grew up in the neighborhood behind that shopping center) at least a dozen times.
The craziest encounter I have had, was hanging out with the Mountain from GOT once afternoon when I lived in Austin. I went to the "Startup Olympics", which was a bunch of drinking oriented games where startups competed with each other because a few of my friends were competing, and they had hired the Bodybuilder actor to make an appearance.
A female friend starts chatting him up, they talk for a while, and then we head back to my buddy's place to continue the day drinking. We ordered pizza, so when there is a knock at the door we think nothing of it, but its turns out to be the Mountain and his manager. Turns out our friend had invited him to hang out with us afterwards, and he took her up on the offer. Dude hung out with us for about two hours, drank some beers, ate some pizza, told some stories. and let us take (non-drinking) pics with him. Pretty cool guy.