I'm going with Rem Koolhaas. http://en.wikipedia.org/wiki/Rem_Koolhaas Not too mention he just designed the new Wyly theatre in Dallas! Looks great and only a mile away from me. http://usa2010.org - "Wear your support for the USMNT!"
Since I have a pretty hopeful bid out to get on a project with him I will say Norman Foster. Well at least until Zaha Hadid and Santiago Calatrava get back to me. But this is a leading question because the old school firms like McKim and SOM can still put out some amazing stuff
I'm not a big fan of Koolhaas (just a matter of taste). My favourite is Ben van Berkel of UNStudio who designed the iconic Erasmus bridge in Rotterdam notably. http://en.wikipedia.org/wiki/Ben_van_Berkel
I'll hold back on listing a few of my favourites, simply because I can't think of too many off the top of my head! However, I to am not a big fan of Koolhaas. I appreciate his forward-thinking and ideas, and understanding or interpretation of society and architecture, but am not a big fan of his actual works or the way his projects are executed.
jean nouvel he's so eclectic; none of his buildings say "nouvel", each is its own statement. here's the musée du quai branly: he does just about everything including social housing where his apparently successful idea has been to get away from the standard of X 15m2 bedrooms with X/2 bathrooms, 8m2 kitchen, and a (15 + 3x)m2 living room, all under rigorously identical 2.5m ceilings, and a 1.5m*2X balcony just to say you're not putting people into rabbit hutches. his apartments are 30% bigger than the norm, and each one original, even dramatic. the overcost is made up by leaving the interiors more or less brut de coffrage, leaving the finishing to the inhabitants. the result? when neighbors come over instead of the depressing realisation that all the places are identical, they're enthused about all the differences, and your own personal touches. and a tickytacky box becomes a home, a bit of magic not even le corbusier with all the talent and good intentions in the world, could manage.
instead of answering here i invite you to read this thread and perhaps continue there? http://www.bigsoccer.com/forum/showthread.php?t=477396
I'll throw in Glenn Murcutt. Although he's now got to that status where it might not be considered "cool" to like his work in schools here, his design methology resembles my own way of thinking, and his end products make great iconic Australian architecture.
those somehow remind me of the house jean prouvé built for himself in the hills above nancy... a self-taught architect whom men as diverse as corbu, mallet-stevens and FLW all admired, a pionneer of prefabrication and industrial design, he made his house out of all the odds and ends he could scrape together when his factory closed down, and that makes the thing all the more inspired, and inspiring. arte did an outstanding documentary on this house in their fabulous ARCHITECTURES series, unfortunately only available in french.
