I think the worst meter (in terms of accuracy) I’ve had is the one I’m using at the minute; the RF version of the Bayer Contour (which I reviewed over here https://www.shootuporputup.co.uk/2009/06/review-bayer-contour/). Most of the time it’s fine, but the other day I tested my BG and it came out as 26.1. I thought to myself “blimey, I don’t feel 26.1”, so I tested again and Lo! I was actually 7.7. This has happened enough times that I’m beginning not to trust the damned thing.