As far as I understand it:
1) Nothing much. Nothing at all, in fact. That's the thing about relativity. The person being accelerated wouldn't feel any different - they'd only feel the acceleration. To anyone standing around outside the accelerator, you'd see the usual relativistic effects - length contraction, the acceleratee aging more slowly, that sort of thing. But otherwise, nothing - unless, of course, a brick wall got in the way. Also, when they're moving that fast - don't blink or you'll miss 'em.
2) Neutrinos would be fine - they ignore pretty much everything. You'd need a REALLY intense neutrino source nearby for much to happen - like a supernova in your solar system. During the average person's lifetime, the odds are that just ONE neutrino interaction will happen in a given person's body. That's over eighty-odd years, and despite being constantly bombarded by a flood of billions of neutrinos every second from the Sun (plus sundries), twenty-four hours a day (they pass straight through the Earth).
The other stuff - not fun. OzOz is not volunteering to be placed in a beam of electrons, protons or neutrons.