Hmm, that's a really interesting question actually. My focus is in mortuary archaeology, so I'm an arch/bioarch fence-sitter of sorts. Admittedly, I have a big ol' soft spot for theory: learning about theories, debating theories, critiquing them, & so forth. It's amazing how much overlap with philosophy (of science, among other things) there can be.
My two first thoughts were Michelle Hegmon, who's at ASU, & Ian Hodder, who's at Stanford. Hegmon coined the idea of "processual-plus" theory, that is, the blending of processual & post-processual theory that seems to be en vogue in American archaeology. I'm interested to see where the whole processual-plus perspective goes, & there are many thoughtful critiques & criticisms of it out there, namely from scholars who lean in the feminist and Marxist direction — that is, theories that make a point of examining something specific in its own right (women/gender, economics/social struggle) & are also politically charged. Hodder is very much a post-processualist, so I'm not sure he's quite on the cutting edge of theory anymore, but he is a theoretical heavy-hitter f'sho. I now Barb Voss is also at Stanford, & she does some cool theoretically-bent work on ethnogenesis & gender in archaeology. Not sure what the rest of the Stanford faculty is like.
Pretty good timing, actually: I had a reading-based discussion in a seminar today about the role of ontology in anthropology, which seems to be a very new niche of interest, but a super interesting one (to me, at least!). Martin Holbraad, who's at UCL, came up often, as did Severin Fowles, who's at Columbia through Barnard College. Columbia's faculty has lots of familiar names for me that rang a "theory!" bell in my brain, but I think most are cultural in focus. Hmm. Otherwise, the other names that came up belong to people who are in Denmark, Brasil, & other places where language may be a barrier. The link that clicking Holbraad's name leads to may offer other people, too!
Theory is so, so broad, even in archaeology alone.. it just depends on what kind of theory you're interested in, I guess. Not sure how helpful I was, but, as I said, I love all kinds of theory chitchat, so I'm interested to see what other names & programs pop up!