For me it's the .45ACP
I learned to shoot on a 1911, my first gun was a 1911, and I used to love shooting it, but I've found that I've moved on. I have nothing bad to say about it's performance, I just like shooting other things more.
Also, you're limited to a single stack mag, or a potato handle.
Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety. ~B. Franklin