Another vote for the Campagnolo Nuovo Record. Preferably 1976, if only because that's the year I started cycling "seriously." All I could afford at the time was a Motobecane Mirage with decent Suntour and other components, one step up from rock bottom (Huret, I think, on the Nomade, which I also had briefly)... while lusting over the Campy goodies in the magazines and stores.
It just looks right... as long as you need only a corncob freewheel with five cogs and don't plan to shift much in a hurry.
I enjoy this summary from the excellent
Disraeli Gears site:
Frank Berto caustically comments that the Campagnolo Nuovo Record rear derailleur shifted poorly, but was so well constructed that it would keep on shifting exactly as poorly - forever.
In terms of form and function, I must be partial to both the Suntour GPX Accushift and Shimano 600 (6401) Tricolor rear derailleurs, because I use both. They're cosmetically similar: blue/grey accents, mostly smooth lines, rounded edges, shrouded pulleys. Pretty simple, reliable, subdued good looks.
Both work equally well, once the Suntour drivetrain is tweaked. After piddling with the GPX RD for the first year, fussing over minor issues, I realized the main problem isn't the derailleur but the original Suntour chain (awful, the crudest built chain I've seen on a modern bike) and Alpha freewheels. Switching to a KMC Z72 chain and SunRace MFR30 or MFM30 freewheels resolved all my shifting complaints. And I replaced the draggy original sintered bearing pulleys with excellent but affordable Tacx Delrin sealed bearing pulleys, which I even prefer over Shimano Centeron.
And I have some Dura Ace 8 and 10 speed stuff, but for some reason haven't installed 'em yet. That was my 2020 project but all I wanted to do was ride my bike, so the DA stuff is still in a box waiting for that round tuit.