My all-time favorite bullets continue drop from single-cavity moulds: Lyman's 454190 and 457193.
(Hmmm . . . didn't both those bullets have their origins in 1873? Says much about my gun preferences.)
Not necessarily my favorite .30 caliber bullet, but the single-cavity, ancient and ventless Ideal 308291 was very versatile, in that it worked more than adequately in the Winchester Model 94, the very early 1898 Krag, and the 2-43 dated 03A3. When I finally found a Lyman 311284, guess what?, it was a single-cavity. The Krag, for which the bullet was designed, was gone by that time so never got the chance to see if it would better the 308291. However, it is arguable the 03A3's favorite bullet.
I must have shot several thousand of Lyman's 452374 that were dropped from a single-cavity mould, and still have over 500 loaded.
Yep, even for mass production I like single-cavity moulds.