Unfortunately, I've lost too many friends and colleagues to count over the 45 or so years I've been flying (best guess is that it's about thirty).
A very close call for me involved a biplane that crashed during aerobatics, killing my friend and seriously injuring the other occupant, his girlfriend. I'd sat in the same seat as he did on the aircraft's previous flight and had done similar aerobatics over the same place. I helped push the aircraft out from the hangar just before the fated flight. The AAIB found that a control restriction was the most likely cause.