There are many good discs out there (Buzzz, Nuke, Teebird, Roc, etc.)
I am wondering what disc that you think everyone should try out, and should have in their bag.
I say ESP Zone.
It is a perfect stable short-range disc, but its ability to really skip puts it above most discs around.
Edit: What is a disc that no other disc from any company can replace (Innova Katana, and Discraft Nuke are similar, Discraft Buzzz and Latitude 64 Core are very similar)