Crochet Chunky Twist Torsade Necklace pattern - I feel like this is a good start, and there's a lot you could do to personalize this. Maybe three twists in rasta colors, maybe pink and black with a Monster High pendant, or all black and adding a beaded fringe in the front (I would so wear that).
Here's what you can do with that single skein of yarn that you love so much! I like this idea better than the t-shirt necklaces. Plus it's a great way to show off art yarn like this http://farm6.staticflickr.com/5016/5477576794_021e7e3dea.jpg