Many climbing equipment manufacturer’s make nuts. They’re all pretty similar. I use Metolius nuts. I have these because I got ’em cheap, but if I had to buy new I would get Black Diamond or Frost (if I could find ’em). The curved shape of the Metoilus nuts tends to get stuck more offend than the simpler taper of most nuts.
An interesting idea is to rack a mixture of large and small nuts on two biners, so if one is dropped, there is redundancy. I don’t do this, but I might if I had a really minimal rack (read: alpine).
I rack RPs on one biner and large nuts on another. This is the quickest way to get to the right gear. I don’t use oval carabiners because the symmetry makes it harder to tell which side opens, and ovals are heavy and bulky.
If I’m using a gear sling, I usually still keep nuts on my harness. This gives quick access, and reduces overall bulk.