This one is tricky for me, since I haven't had any truly strong negative reactions to yarn in a while. There are lots of yarns I like, and many I'm mostly indifferent to, but I had to dig deep into my knitting past to come up with a truly awful yarn experience. It turns out that in my early days as a serious knitter I made a lot of unfortunate yarn choices; looking at some of my early ravelry projects makes me wince.
What was I thinking? or, Yarn I Loathe
In 2006, I acquired a lot of cheap sale yarn from a craft store in the neighbourhood that was going out of business. I was just starting to get back into knitting in a serious way, and I was figuring it out as I went along. (Not that this is a bad way of approaching learning!) This was before Ravelry, so I didn't have the yarn database at my disposal.
Hence, my foray into using Bernat Denim Style. This is an acrylic yarn plied with cotton that I'm sure has some uses, but the following is not one of them.

I made Picovoli, a cute tee by Grumperina. This was a bad idea. First of all, the yarn is aran weight and the pattern calls for DK. I thought I was being clever and made a smaller size to compensate - this only sort of worked. Secondly, the colour is pretty terrible on me. Beige streaked with white? What was I thinking. Anyway, the pattern is awesome, and maybe one of these days I'll attempt it again, but in this yarn it quickly became mishapen. I tried wearing it a few times as a t-shirt and as a vest. It wasn't great for next-to-the-skin wear because the acrylic made me sweat and didn't let the moisture escape easily. Gross. In any case, this was a lesson in inappropriate yarn choice for a given project.
But enough negativity.
Now I Gush about Yarn I Love
There are so many yarns I adore in varying fibres and price ranges.
It is no secret that I love Manos del Uruguay Silk Blend - the softness, the drape, the gorgeous colours whether semi-solid or variegated... Ah. I could go on. Because this yarn is not very hard-wearing, I don't think I'll ever make a sweater with it. However, I've decided I want everything I wrap around my neck to be this soft, so I've made two scarf-like things with it.

The first, pictured above, was My So-Called Scarf by Allison Isaacs. It's tricky to find stitch patterns that do the constantly changing colours of this yarn justice, but this pattern is brilliant for variegated yarns. More recently, I made my Danube Cowl (pattern forthcoming, etc etc plug plug) with a semi-solid colourway.
I haven't made these yet, but I think the Honey Cowl and Holding Hands, Feeding Ducks scarf look great in the variegated version of this yarn as well. In my queue!
2KCBWDAY1