Making a tank top out of that t-shirt? Well don't throw out the sleeves, because you can make one into a soft cloth choker to decorate however you like! This is super easy, and really fast! When I made my first one the longest part was taking the pictures of each step! XD
Pardon my way classy appearance in the second photo, I'd just washed my hair and I figured it would get in the way of seeing the actual choker anyway so I left it up in my TurbieTwist.
Get a t-shirt (and this is important, if it's a fancy shirt or in a fabric without much stretch potential this will be harder) preferably in your size, and smooth one sleeve flat.
Cut right along the inside of the sleeve's seam (the side closest to the armpit) one side at a time. It might be helpful to cut the side first, as shown in the picture.
Since jersey knit fabric doesn't really fray, you don't have to make seams or serge the edges unless you really want to! Make sure that the strip you now have goes all the way around your neck with a little bit of overlap just in case, so your snaps have room to meet (this depends on what kind of closure you're using). If you stretch the strip a little at a time after testing it out it will gain a bit more length as the fabric stretches a bit naturally. If it's too long, cut it a bit at a time to fit (It's important to do it gradually or you might cut too much and have to add extra or start over with a new seam).
Now, put on whatever kind of snap you like. I used stickyback velcro, since I'm using mine just as a costume piece and the sticky side of my velcro pieces is really strong. Be sure that you put your snaps on different sides (wrong side/ right side, or inside/outside) of the fabric or they won't meet when you fasten it!
If you want a plain choker, you're done! I needed to put a charm I made on mine right in the middle, so I fastened the choker and folded it in half to find where the approximate middle was, and then pinned it. You can do this as many times as you like as long as the sewing needed for your decorations doesn't shorten the length of the choker, since we've already measured it!
Once you have it decorated as desired, you're done! Now you have a nice, comfortable piece of jewelry to wear for all sorts of occasions.