Well...If I look back and reminisce:
The 270W is the most frequent cartridge by far of all my deer hunting friends and acquaintances.
Also bunch of 30-30s, 308s, 30-06s
I've seen a few 35 Rem, 300WSM, 7-08, 243 Win, 257R, 6.5 CMs. so I would no put any of these on the "over-looked" list.
I've never hunted with anyone that used a 338 Fed, 300 savage or 6.5x55 Swede
I've only seen 1: 250 Savage, 7x57, 7.62x39, 7.7x58, 8x57
I'd leave out the 338 Fed, 7.62x39 and the 7.7x58. So..............
My top 5 over-looked deer just from experience in order of my preference:
8x57, 7x57, 6.5x55 Swede, 250 Savage, 300 Savage
I would feel very comfortable using any of these.
And even though I would reload'em, I think I could still find factory ammo for the 2 Savages.
Maybe hard and probably be expensive, that's why I listed them 4th and 5th in preference.