I find that older is usually better...
Do they have to be rifles that are still in production? Presuming no...
1905 Mannlichers are some seriously gorgeous guns. Slim little full-stocked carbines, butterknife bolt handles, and that elegant schnabel nosecap set the standard for bolt-gun elegance in my book. Modern guns with similar styling are pretty nice, but the originals are very hard to beat.
Other guns that are nice to look at, but are long out of production (Outside of modern repro's.) are Sharps', Winchester Hi-and Low-wall's, and the Offficer's model Trapdoor rifles produced by the original Springfield Arsenal. (These were fancier versions of the 1873 service rifle that had a semi-pistol grip, a shortened fore-end, and a pewter nosecap built by the gubmint arsenal on a special-order basis for a short time as a perk for officers.)
For a levergun, the original Henry's lack of a fore-end always gave it a clean, no-nonsense appearance that has always appealed to me.
Colt Lightning pump-action rifles also have a very clean, slim silhouette as a result of their lack of a loading-lever and the smallish hand-grip/fore-end.
Another feature that I really like found on a wide range of 19th century guns is the octagon or half-octagon barrel, a look that I think exemplifies the old-school-craftsmanship feel of guns from that era.
As far as modern guns go, bolt-guns have a tendency to kind of blur together for me, as it's hard to cosmetically distinguish the essential features that found on today's highly-refined designs. I do like the proportions on the Browning A-bolt, but not so much as to say that it stands out over guns like the Winchester, Ruger, or Remington.
One gun I find in a class by itself is the Browning BAR. This gun has elegant lines, and a unique hump-backed silhouette reminiscent of the Auto-5 shotgun, but without the clunkiness that a wide 12-guage receiver brings. Put a schnabel fore-end and a half-octagon barrel on one of these, and I'd be drooling all over my shoes.
I really like Remington Model 8 Woodsmaster autos also, but it's because they look ODD, not because they're attractive, per-se. When done-up with top-grade engraving, however, they can look pretty snazzy in an "Early Industrial Revolution" kind of way.
I would say that any given double rifle is the hands-down winner of all, but they don't really qualify as a "factory" rifle due to their mostly hand-built origin.