I've watched several airplanes land gear up. I watched a Harrier crash years ago, and have been present for several agricultural wrecks. I extracted the pilot from one, and put out the fire. I saw a lear grind it's right main gear off once after the tire exploded. I've seen a few airplanes ground loop. Watched a 185 crash on takeoff, once; pitched straight up, then straight back down. I was present when the first of the final five T-38's crashed on the Thunderbird team (Lt. Nick Hauk) at HAFB; that was something like 16 years ago.
I've been in close proximity to several airplanes that have started up with objects in the way, including one person who taxied into his car, and another who nearly hit me with pieces of his towbar.
Numerous ground fires, a number of in flight fires. I saw a helicopter go in once in California. I was present last fall for the wreck (albeit minor) or a government airplane on a training fight. I had an onboard explosion that removed about twenty feet of metal on the back end of an airplane, once. I've seen a few ultralights crash, most not too serious, one fairly serious. Just missed being present when friend was killed in one.
I've been present, and have treated, several individuals who had bad parachute accidents (the last one being in August of last year). I had three landings yesterday that could have easily been termed "crashes"; the result of attempting to land a parachute that I shouldn't have been jumping. I've had one significant parachute crash that resulted in time spent in intensive care, though head injuries have precluded me from remembering seeing most of it.
I was present many years ago when a gentleman attempted to handprop a light experimental airplane with the wing tied down, the tail not tied down, the mags both on, and the throttle set at half. After the airplane ran him over it struck a fuel truck and punctured it. He survived, but I'm reasonably certain he never did that again.
I've been present at many wrecks after the fact, over the years. None are anything one would care to remember.
Aircraft wrecks are much like car wrecks; if one has seen one, one has seen one too many.