at the moment
marti guixe
a lot of droog designers (Jurgen Bay, Hella…)
Thomas heatherwick
Ron arad (his book is good)
Dunne and Raby (also good books)
And Marcel Wanders who is gaining tons of respect in higher fine art circles as well as product design. I also happen to like his stuff, so I am probably biased.
Jonathan Ive, what he is doing with Apple is brilliant. Constantly raising the bar i feel.
Ross Lovegrove
Jonathan Ive
Arne Jacobsen
Eva Zeisel
Dieter Rams
Maybe a good measure would be designers and design firms that have actually made an influence outside the design circles. I.e., IDEO was on Nightline, Rasheed is going to be on the Discovery Channel, and whoever is responsible for bringing IDSA, Coroflot, Core77, and Businessweek together. That is some really influencial stuff if you ask me. I really admire people who can bring other people together like that.
i agree with bebop:
dieter rams
in the 50s and 60s he did all stuff for braun (like radios for example). that was really new and headturning design, because of its clean, minimalistic look. a big step forward in design history. very modern and industrial - things that are normal today - he designed them first.