[rightwingcrazy]

“pass through matter without interacting with it at all.”

Presumably they have mass, so they’d interact gravitationally, at least.

[Red Badger]

“The mass of the heaviest neutrino is roughly 0.05 eV, the mass of the next is somewhere between 0.01 eV and 0.0001 eV, and the third has a mass significantly less than these two values. For comparative purposes, the lightest non-neutrino particle is the electron with a mass of 511,000 eV.”

Neutrino Masses - Jupiter Scientific

http://www.jupiterscientific.org/sciinfo/numasses.html

[Red Badger]

https://en.wikipedia.org/wiki/Neutrino

[Lazamataz]

Presumably they have mass, so they’d interact gravitationally, at least.

Not necessarily. Photons, among other particles, don't.