Sorry, I read JUST the title of the thread and not the actual first post by the OP. it's a bad habit but USUALLY on all it does is restate the title question.
Since he snuck "US" in there, I will change my answers to the following:
Modern: Sig M-11. Didn't have to be general issue, right? (If it does, just rename the thread "Why is the 1911 your favorite US military handgun?")
Vintage: 1911A1. Nowadays, I like the arched MSH better because it makes me have a higher more controlled grip.
Antique: This one is hard to answer. My first instinct is to say the "SAA" but then I think about how long it takes me to empty and reload my New Vaquero. While I know with practice it can be done quicker, the single cartridge at a time system is still slow. So, I guess my pick would have to go to one of the top-break models that took smokeless powder cartridges, strictly because of reload speed in a hostile situation.