As far as I can tell, currently the two best minimal-yet-protective sleeves designed specifically for the rMBP 13" are Tom Bihn's
Cache and Waterfield's
Outback (see also the latter company's other
options). I'm leaning towards the Outback because: a) it looks less generic, and b) I think waxed canvas will protect better than Taslan nylon against sharp pokey objects.
There's also the beautiful and possibly overpriced* felt sleeves by
Hard Graft,
Mujjo and
Pack&Smooch, but at ~$100 once you include shipping, they're more than I'm willing to pay.
My preferred sleeve for my 13" MBA is Acme Made's
Skinny Sleeve, but my 13" rMBP slides out of that too easily because of its narrower body. The
13" cMBP Skinny Sleeve is 2.55cm wider, so it won't work either.
For now, I have a 13" MBA Suede Jacket Sleeve that I'm using to protect the rMBP against scratches. It's slightly loose but does the job.
Incidentally, this thread should really be merged into
this one.
* Particularly appropriate for the 13" rMBP, then? 