Edsger Dijkstra was a pioneer in computing. Yet he lived like a luddite. He did not own a television or go to the movies and did not even own a personal computer until much later in his career! He enjoyed playing the piano and left behind a large amount of papers and documentation - both personal and technical.
Leslie Lamport wrote one seminal paper after another in the field of distributed computing and concurrency. He co-created LaTex and the Paxos algorithm. He then rigorously defined the temporal logic of actions (TLA) which is a mathematically correct basis for a checking a program's behaviour/models at a high level. I took his TLA+ web course recently. The presentation of the course is fantastic. His mirthful yet sincere attitude really shines through in it.
Are there any pioneering researchers who you find fascinating?