I strongly believe that you can never have too many scarves. Or hats. Or armwarmers. Here are three scarves which I've made, a new one each year:
The oldest is the seed-stitch scarf in the middle. It was done back in '04, and the only reason I even know that is because I remember working on it at my mom's old apartment before she moved.
It's knit from that perennial favorite, Lion Wool-Ease, on JPN 10(5.1mm) needles. I can't remember how many stitches I cast on, but there are 20 rows of each color.
When I started trying to expand my crochet knowledge last winter beyond chains and single crochet, I selected a shell and wave scarf pattern from http://crochet.about.com/
It's looking a bit haggard at this point, I've worn it a lot, and I attempted several projects with it before this one so the yarn was already a bit stressed out from being frogged so many times. It's Diamond Diaparterre (50/50 alpaca/acrylic), the same yarn I used for my Clapotis. Strangely enough, as soft and wonderful as the Clap is, this scarf can feel scratchy at times (probably due to all that frogging). The coolest part is how, thanks to the shells, the color pattern comes out in splotches and zigzags instead of stripes.
After that scarf, I fell away from crochet again, went through a few (relatively unproductive) cosplay and (somewhat productive) knitting phases, and didn't come back to it until this winter. I put the purple merino I bought to good use and made the One-Skein Scarf from SnB: The Happy Hooker(which was a misnomer in my case, since it took 2 1/2 skeins).
I never really bother with checking gauges when it comes to scarves and just adjust accordingly to suit my specifications. In this case, I increased the repeats from 3 rows to 5 and added an extra scallop on each end to compensate. I'm still working on my crochet technique and am much better at working in the round than straight; my chain edges always seem to be tight and make the whole piece curve, even when I cast on with larger hooks (as I did in this case). Maybe a good blocking would fix it, but it doesn't matter too much when I wear it, so it's really not a priority.
I had 1 1/2 skeins left over, so I made a hat to match:
It's the Blue Star Cloche from Hook Me Up! Crochet, although the star on it is actually this pattern and made out of leftover Clap yarn. I used an I hook instead of the recommended H since I wanted it to be a bit longer.