Honestly? a Benchmade 940 last year. I was super excited for it too but it was insanely dull out of the box compared to my insanely sharp OTB Grip and it developed blade play in minutes of playing with the axis lock. Every time I adjusted it, it just loosened up again. I was just extremely let down by i especially after all of the amazing things I heard about it on here. I ended up trading it for a ZT. I like tactical style folders more than gentleman/traditional style anyway.
My 940 was the same.
I sharpened it on my sharpmaker and threw a little loctite on the pivot. It still has a teeny bit of wiggle but I really like it as an edc.
Worst knife I've purchased was the crkt m16-14sf. I actually really liked it out of box. It was sharp, I could wave it from my pocket, it had a flipper for deployment as well.
But the liner lock broke in REALLY late after a few weeks. The auto lacks system with a liner that is kind of f'd up became way to cumbersome for me.