Gabapentin
"I was prescribed 100mgx3 Gabapentin increased to 300mg x3, worked a little on sweating but after a few months I noticed I had gained weight.  Soon it was spiraling out of control and before I knew it, I had gained almost 20 lbs!
 Discontinued use, (I had no withdrawal). Went back to my normal size in a few weeks and tried to take the Gabapentin again. Seemed okay at first, then the weight came back again. I am also on Amitriptyline, which I saw some one mention earlier. Also had dizziness and difficulty urinating. Nothing is worth the weight gain."