HK VP70z. I was always curious about them and thought they were neat. Saw a used one in store about 7-10 years ago. Price was decent and it was in not bad shape. After handling it I decided against it.
It only had the one mag IIRC so finding others was going to be a PITA. Plus, I knew going in it was going to have a heavy trigger and be of limited use to me ie safe queen.
In retrospect, I probably should have as it is the closest I'll get to a Walther PP/Sig P232 (which I'd really like) in my lifetime, short of one of the restricted frankenbarrel ones.
I've also been sorely tempted with a couple Browning BDM's that pop up here time to time, but again a semi-rare gun and mags keeps me from "pulling the trigger".