The second of the three cardigans I think any well-rounded closet should include (the first mentioned being the V-neck cardigan) is the ultra-classic crewneck cardigan. Of course, the key ingredient with this one is the neckline itself — the shaping needs to be impeccable, with the front neck lying flat even when not buttoned (rather than poking you in the neck or flapping awkwardly forward at the top). Here are some top candidates for knitting your own—
TOP: Eva by Kim Hargreaves is like the dream vintage-store score, perfectly shaped in every regard and written for a lace-weight mohair blend; set-in sleeves, worked flat and seamed*
MIDDLE LEFT: Shore Cardigan by Carrie Bostick Hoge is the quintessential worsted-weight stockinette cardigan; top-down seamless, raglan sleeved, with that tidy garter-stitch border detail at the edgings** (Not being a fan of the droopy hem trend, I personally would omit the short-row shaping there)
MIDDLE RIGHT: Dory by Amy Christoffers is also worsted weight, with just a bit of texture on the yoke; knitted flat and seamed, with set-in sleeves (free pattern)
*Unfortunately only available in the book Smoulder, but it contains several pitch-perfect basic cardigans, among other things.
**Currently only available in the book Swoon Maine, but expected to be sold individually in the near future.
PREVIOUSLY in Make Your Own Basics: The V-neck cardigan