What cookie scoops are best?

I think Piazza Scoops are the best. Practically indestructible. See http://www.williams-sonoma.com/products/piazza-ice-cream-scoop/
and others

I have several of the Zeroll ones in different sizes and after years of use they still work great. Not cheap but sometimes you'll see sets of the most common sizes available and those can be a good deal.

I use ice cream scoops that I purchase at a restaurant supply store. I don't know what brand they are, but they are quite sturdy.