[Nexus 6P Accessories] LuckyDragan:
Long response incoming:

I initially bought a official microfibre Adopted case (in carbon) from Google along with my N6P (aluminium). I paid full price for it, but I thought it was worth the premium for an official case and the design was cool and unique. Massively underwhelmed when I received it, because it's nothing more than a generic TPU case with a thin "sticker" of microfibre on the back, which I sensed would be prone to staining and, over time, peeling. The fit was also really tight and button presses weren't that responsive. I decided in the end that the Nexus branding wasn't worth the premium, so I returned it.

I then ordered a charcoal Diztronic case. I've had good experiences with Diztronic in the past, having used their case on my Galaxy Nexus as a daily driver. It was cheaper than the Spigen Rugged Armor and I appreciated the minimalist aesthetic, not being a fan of the faux carbon fibre pattern on the Spigen. The fit and finish was great, and the buttons were clicky and responsive. My only minor niggle was the cutout for the camera sensor wasn't completely accurate, as it cut off part of the circle surrounding the sensor (100% an aesthetic oversight with no impact on function).

I then bought a Speck Candyshell Grip (in white) during the Black Friday sale, when it was 50% off. Definitely my favourite case of the three I've tested so far. It provides the most protection (being a dual-layer silicone and polycarbonate hybrid), looks striking, and, as the name implies, provides a ton of grip.

I've had a Speck Candyshell on my iPod touch and over 4 years later, it's still kept my iPod in perfect condition. The case itself is scratched up and turned a bit off-white, but I haven't exactly been gentle with it (having taken it traveling and camping) so I'm confident in its protective capabilities.

I'll likely be rocking the Speck case as my daily driver for the time being, and I'll only swap back to the Diztronic when I want a more toned-down look and slimmer profile (maybe if I'm at a fancy event wearing slacks).

Finally, I also pre-ordered a white Crash Guard + Project S from Evolutive Labs when they offered 25% off the first 50 pre-orders. IMO this would be the solution to preserving the Nexus's original design and aesthetics, while still providing a lot of protection (if the demo videos are any indication). I have no idea what Project S is, though (hopefully some kind of transparent skin, though they said it wasn't going to be made of the same material as the Rhino Shield).

I have a tempered glass screen protector from intelliARMOR protecting the front (second generation/first revision, the model prior to production of the two distinct "case-friendly" and "edge to edge" versions). It's been fine with both the Diztronic and Speck cases, though I'm curious as to whether the edge-to-edge versions might also be compatible with the Speck and Crash Guard, as there's just 1 mm between the edges of the cases and screen protector, where I find dust and grease can get trapped in between.

If you're looking for clear cases, there're Spigen's Ultra Hybrid and Neo Hybrid EX cases. The Ultra Hybrid is a single-layer case with a clear polycarbonate back framed by TPU along the edges. I wouldn't recommend it personally because I've heard that clear TPU will stain over time (as likely what happened to your original case), and the visor is completely exposed and thus prone to scratches.

The Neo Hybrid EX consists of 2 pieces: a clear TPU shell and a coloured polycarbonate bumper (essentially, the reverse of the Ultra Hybrid). It looks to be the best clear case I've seen in terms of protection (as the visor is actually covered), but I don't know how the clear TPU will fare over time, whether it will also be prone to staining. I'd wait on reviews for this case before ordering, and for it to be listed on Spigen's Amazon store, which will likely be cheaper than buying it off their main website or eBay store.