I've done a lot of crazy beers, but one of my most memorable batches was a traditional Gruit beer brewed with yarrow, mugwort, bog myrtle, wild rosemary, and "dry-hopped" with some heather tips. It almost tasted like a sour to me at first and I was afraid it had gotten infected until I decided to make a tea with those same herbs and realized that that was the same flavor that they'd all contributed to the beer - sour-ish if you will, but not true sour if that makes any sense. It was an interesting experiment that I very much enjoyed drinking, though for any newbies to the craft beer scene who don't have adventurous palates, I wouldn't recommend it.
I'm actually thinking about brewing it again soon as some of my friends were talking about it the other day wanting to know if I'd make another batch of it... Maybe later this summer?