I have a favorite cast-on. It's kind of weird. Other folks have used it I'm sure, but it was an idea that I had that worked out really nicely. You cast-on over two needles (or one really big one) and then you immediately do a ton of double increases.
When you work in stockinette stitch you get a nice little star cluster effect that runs all along the cast-on edge.
It does however have a natural curve and tightness to it. Frequently knitters will worry that it's too tight. It's not! I promise. When you go to block the design it will block out into the perfect crescent edge, like you see in Longfellow below:
Or in Lawsonia:
You can even use it in garter stitch shawls like Jovia, although the cluster effect is not as pronounced.
What's your favorite cast-on?