Depo-Provera
"I had been using Depo for about 3 years.  I spotted for almost a year and then my period went away all together.  I had a 5lb weight gain, which isn't so bad.  I had a decreased libido.  But I think worst of all was that I had terrible acne.  I've never had acne like this.  I've been off the shot now for 8 months and I just got my period back (though irregular) about 2 months ago.  My acne is still there but seems to be getting a little better.  As a birth control, it was easy and it worked."