I've never been a personal student or close personal friend of any super famous martial artists, but I've been to seminars with:
Stephen Hayes
Masaaki Hatsumi
Doron Navon
Renzo Gracie
Royce Gracie
Carlson Gracie Jr (who awarded me my BJJ black belt)
Carlos Machado
Dan Inosanto
Herman Suwanda
Chai Sirusute (who awarded me my Thai Boxing apprentice instructor license)
Sakesem Kanthawong
Jongsoonan Fairtex
Neil Adams
(also a host of other instructors who are relatively prominent within their fields, but aren't necessarily so well known to the wider martial arts community - I've lost count, but I've attended well over 100 martial arts seminars over the years.)
There are also a few former UFC fighters that I've trained with along the way:
Jorge Gurgel (friendly acquaintance, been to a bunch of his classes, did some sparring with him before he started seriously competing)
Mike Patt (my first full time BJJ instructor, awarded me my blue belt)
Rich Franklin (rolled with him once, nice guy, he dismantled me effortlessly but was polite about it)
Dustin Hazelett (rolled with him once, Jorge called out "hey Tony, see if you can keep him from triangling you". Dustin proceeded to triangle choke me over and over again without my being able to do a thing about it.)
Junie Browning (casual acquaintance, used to train at the same gym, did some drilling together, was complementary about my skills)
As DD notes above,
@Buka is the guy who really knows all the famous martial artists.