Just got my $8 Bear Motion Sand (black) back shell case for iPhone 6.
I find it super grippy, but not like sticky rubber, has a high quality texture, feels good in the hand. It's sturdier than the ebay/china slim flimsy shells, but still minimal. Feels very solid on the phone. If it had top and bottom coverage it'd be the perfect slim case for me.
If you tap the top of the phone directly on a table, the plastic back contacts it, if you tap the bottom of the phone on a table there is some plastic contact, but not as much as the top, if that makes sense. There is a little overhang of the flat edge of the back cover at top and bottom.