Glass and silicone. Glass is completely safe, as long as you take care of it and don't drop it on a surface that will break or chip it then you have nothing to worry about! The ones sold here aren't made of the crappy quality some kitchen drink glasses are made of so you aren't going to crush them when gripping them and using them.
Tie between glass and silicone, depending on what I'm feeling that day. If I want to it to feel more realistic I got with silicone for the softness. However, if I want to target my g-spot and ejaculate glass is my best choice because of its rigidity.