Which glue/adhesive to use for Swarovski flat-back crystals?

I just bought a BUNCH of Swarovski flat-back crystals, and I want to glue them to differnt objects of mine. For example, leather, metal, denim and plastic. WHICH GLUE or ADHESIVE IS THE BEST TO BUY FOR THE CRYSTAL TO STAY AND LAST almost forever =) Thanks!

I have a whole bunch of Swarovski aninmals and flowers and unfortunately no glue will hold the crystal. You should ask a Swarovski Dealer what you can use, because if an animal is broken the only one who can put it back together is a dealer.

Apply Swarovski Crystal Flat Backs (Non Hot-Fix)