A few people who have guided me down the years... By the way, there's now some nice research into why mentoring matters.
Scott Anderson
Scott was my Ph.D. thesis advisor at the University of Washington. His interests range from quasars to compact objects, and it was our shared interest in the latter -- along with how well we got along -- that made him an obvious choice to supervise my thesis. And yes, he is as low-key as his webpage suggests...
David Helfand
...unlike David, whose webpage does him no justice at all. David has known me since my undergraduate days, and been a constant source of advice and direction (not to mention great food) all along. (I don't think I have ever seen him in a bow tie, however.) Hopefully when he retires from running one university (not this one -- here he just runs the Department) we will finish some of the research on supernova remnants we were supposed to do years ago.
Dave Green
Speaking of supernova remnants, Dave was my M.Phil. supervisor at MRAO, in Cambridge, England. He is well known for his catalog of supernova remnants, and continues to be an active researcher in that field. Unsurprisingly, I did my M.Phil. research on a supernova remnant -- perhaps the most famous one of them all, Cassiopeia A.
Kiriaki Xilouris (or Xiluri!)
Kiriaki was my REU supervisor at the Arecibo Observatory, still one of my favorite observatories. The time I spent working with her first in Puerto Rico and then on my senior thesis was one of the major reasons I decided to (try and) become an astronomer. She is now on the Geosciences staff at the University of Arizona; I saw her in Tucson recently for the first time in something like 12 years when I gave a talk there.