Most adventurous restaurants in Chicago?
There have been several articles on the subject and entire TV shows (Andrew Zimmern, Anthony Bourdain). To follow up on jbontario's point, perhaps if you had posted some ideas based on your reviews of those it wouldn't have seemed like we were doing your homework. I'll give you a couple of hints though, to be hospitable: Most focus on unusual ingredients like bugs (e.g., at Sticky Rice), and small, family-owned ethnic places. The fine dining market here is very creative, and in addition to the three mentioned by W42, I'll add Next, based on their every four-month changeover. The upcoming Vegan menu might not seem as adventurous (read "gross" to timid palates) as The Hunt or Kaiseki, which featured squab brain, heart tartare, and whole fish skeletons.
I'm not sure whether you mean adventurous as in "weird ingredients" or whether you mean creative, non-traditional cooking, or whether you are talking about the whole experience being different.
But off the top of my head, I would say Elizabeth for fairly unusual ingredients gathered in the wild all served communally with some fancy techniques. Schwa and El Ideas don't necessarily focus on unfamiliar ingredients, but in both places the chefs themselves serve diners very creative, borderline playful, food in a party-like environment and BYOB.
If you want to focus on sourcing unique seafood, Katsu can have some pretty special stuff if you call ahead.