Fucking scales. I have one I got from amazon for $25 that has worked pretty well for 4 months. Rechargeable, has an app and tracks your weight. 4 days ago, it showed I had gained 2 pounds in 2 days, which is pretty much impossible, since I was following the exact same regimen every single day. No water weight gains.
So I weighed myself again 5 minutes later and I was down 1/2 pound. I noticed one of the base corners was in a grout line, so I moved the whole thing to where every base was sitting on a solid tile. Weighed myself again...back up 1 pound. So I moved the scale around to different places in the bathroom and got a bunch of different weights. And the best part? Our maid moves this thing to a new place in the bathroom every week when she cleans. So, disgusted, I shoved this thing across the bathroom floor with my bare foot, it hit the tile wall and broke into 10,000 glass pieces. Fucking piece of shit.
I walked down the hall to my girlfriends bathroom, used her scale, and it showed I'm down 1.2 pounds. And now I'm using that one every day now.