When you're crunched for time and money for a Halloween costume, consider going as a vampire. It's easy to make your own vampire fangs without spending a lot of time. They're simple to make, and you can design them yourself.
Rinse an empty white dish-washing liquid bottle, and make sure all the soap is out.
Measure the distance between the two teeth where you want your fangs to go.
Draw a rectangle on the curved side of the bottle that is 1/4 inch wide and the length that you measured in Step 2.
Draw two fangs on the front of the rectangle about 1.5 inches apart. They can be as long as you want, but 1/2 to 1 inch is typical.
Cut out the fangs with scissors or a box cutter.
File any sharp edges or rough spots with a nail file, and wash the fangs. Place them in your mouth with the curve in the roof to test for a good fit. Trim as needed.