1) Theory "Elondra encase colorblock turtleneck" (via Bloomingdale's) (pictured left). Made from a cotton / spandex blend, this turtleneck is mainly a deep, deep blue ("marlin") with black contrasts at the end of the sleeves. At $105, it is expensive for a turtleneck, but I think it would look good under a suit during the winter. It also comes in a light blue with dark blue contrasts.
2) Hinge "scrunch neck sweater" (via Nordstrom) (pictured right in the black). The sheer, cotton, stretch turtlenecks seem to be everywhere this season. I especially like Hinge's because the neck can be turned down or simple "scrunched" and because it's a little thicker than the paper-thin turtlenecks that Gap ($26, or $17.50 each if buying two or more) and J.Crew ($29.50 each) are offering, so it can be worn alone or layered. The sweater is 100% cotton and comes in "dark feather" (brown), castlerock (grey), navy, plum, and ivory in addition to the black. It is $48. Nordstrom also carries the turtleneck in a more stretchy funnel-neck version (also made by Hinge); the funnel-neck version is $38. James Perse also has a stretch turtleneck, available via Bloomingdale's here ($74), as does Splendid, available via Bloomingdale's here ($51).
3) White House Black Market "sculptured elbow-sleeve turtleneck" (pictured left). Made from 76% viscose and 24% polyester, I like that this turtleneck's sleeves hit at the elbow, which I think allows it to dress up jeans or a skirt more than long-sleeved turtlenecks. The fabric is very slightly ribbed and there are cuffs at the elbows, making it a bit more dressy. The turtleneck is $68.
4) My all-time favorite black turtleneck is Gap's "jersey turtleneck sweater." It comes in black, navy, heathered green, honey brown, white and grey. It is on sale for $29.50.
Guys can and should wear turtlenecks too. In fact, one of my best male friends wears turtlenecks all the time when not at work, and they look great. He gets his from L.L.Bean, right here; same in women's is available here; both men's and women's turtlenecks are $15 each. Lands' End has similar for men here and for women here; again, both men's and women's turtlenecks are $15 each.
On the higher end for men, there is also this viscose/cotton blend turtleneck from Emporio Armani (pictured right), which is on sale for $148 (originally $245).