I've owned a bunch of micro 9mm's over the years. But my current one is my favorite - a Sig P938 Legion. AKA my "mini-me 1911".
Extremely tiny and thin (it carries in my pocket where the P365, PPS, Shield, and XDS all printed too much). All metal construction (a personal preference), nice trigger, and same manual of arms as the 1911. Recoil can be a little spicy though.