The Rekt grinder is the best grinder for your buck. It has a non-limited lifetime warranty.
Its square tooth design allows for a fluffier grind. The one piece top means the teeth are almost unbreakable. The magnets are the strongest.
The cross knurling means you don't lose your grip even with the stickiest of grinds. The Rekt grinder is bar none better than a Shredder, and it's cheaper.