I figure since I started this, I should contribute some ideas:
Once, for a "cultural potluck" at my office, I brought in Bubble Tea (I'm Taiwanese). I've never made it but had always wondered how hard it was really to make it on my own. I ended up making way too many bubbles for the amount of tea I'd prepared, but people liked it and had fun. Good response.
Alternatively, we had another potluck which I took as an opportunity to make pulled sourthwestern pork, which I had never done and would have never done so since I rarely cook meat. Again, good response.
Similarly, I had friends over one time and prepared lamb chops with a basil-pea puree. Again, this let me practice my meat prep skills and also do a little mad-sciencing to figure out how they made the similar puree at Boka. It was delicious and looked beautiful. My friends were very pleaseed.
And, only last week, I brought in a cake to a dinner that I got from the bakery at City Fresh. It was filled with hazelnuts and pastry cream and had an unpronouncable name. I never had had it, so took a gamble given the other things I've tried from their bakery. It was delicious and I'd get it again in a heartbeat.
So, I suppose, I use these opportunities to not only surprise my friends, but also to surprise myself. Fun for everyone!
These pretzels are making me thirsty...