If you're using PVC, any cement rated for PVC will be effective. If you're using acrylic and PVC, Weld-On #16 will bond PVC to Acrylic or acrylic to acrylic. The #16 is a gel, for fast results Weld-On #3 or #4 works well on acrylic to acrylic bonds
I think the point widcat was making is that which glue you use, will depend on what material you are usnig. Regular white PVC uses a much different glue than clear acrylic.