I use Slime currently, but never had any brand fail under reasonable use. I had a piece of rebar go in a tire once, and I put six plugs in it. Got me home, but it had a slow leak.
edit:
This is more or less what I have, but I don't have the rubber cement...
Whatever you get, don't get the kind that isn't a T handle, and the forked plug inserter is MUCH better than the hook style.
edit:
This is more or less what I have, but I don't have the rubber cement...
Slime 11-Piece Deluxe Tire Plug Kit with Plug Bond - 2040-a - Walmart.com
Buy Slime 11-Piece Deluxe Tire Plug Kit with Plug Bond - 2040-a at Walmart.com
www.walmart.com
Whatever you get, don't get the kind that isn't a T handle, and the forked plug inserter is MUCH better than the hook style.