For the most part the "nonsterilizable" materials are materials that would degrade if exposed to common sterilization techniques. The porous materials cannot be effectively chemically sterilized because of the problem of bacteria getting into them, but other materials would melt or degrade if exposed to heat or sterilization agents (many plastics fall into this category). Toys with mechanical components can also be damaged by the sterilization environment, so even though your vibrator may be silicone sterilization possibilities are limited (they can generally be effectively sanitized with bleach-water, though).

Some other limited items are metals, as stainless steel and aluminum can be attacked by bleach solutions (boiling works, and for stainless you can dip and rinse in bleach)

If you have a high-power gamma ray source then most objects can be sterilized, even if they are porous or not resistant to heat, but that's your only choice for some of them and the equipment is usually difficult to come by. less