M27-2, 5" (Cadillac of the S&W line, topstrap checkering declares it, superb balance, the classic Smith)
M57 no dash, 4" (very close second to M27, and I like the caliber better and this barrel length carries well. Ideal frame size for the .41 Magnum; frame too light for the .429 Magnum)
M57 no dash, 6"
M17 no dash, 6" (K22 - every S&W afficionado needs one)
M63 no dash, 4" (great gun for packing, fishing companion)
I know this was revolvers only, but here's a Smith and Wesson must-have:
M41 (thank me later - I've had mine for over 30 years and grin every time I shoot it)