A couple months back, I got into yet another debate with someone about why I hated Batman using a gun in
Final Crisis. I meant to post this at the time as a canonical response, but got distracted with IRL stuff and general geekery at
my Two-Face fanblog. Besides, I figured this might be controversial, since it's a controversial real-life topic combined with a controversial comic topic, taken from a comic that was deeply controversial at the time it was released:
Batman: Seduction of the Gun.
B:SotG was an anti-gun one-shot published as a benefit issue for the
John Reisenbach Foundation for gun-control education activities, a fact which wasn't revealed to readers until the end. DC was flooded with angry letters from gun owners and Second Amendment advocates, many of which were published in the early
Knightfall issues. Many letters were along the lines of "My heart goes out to the Reisenbach family, what a tragedy, BUT STILL GUN CONTROL IS BAD I FEEL BETRAYED FOR ACCIDENTALLY DONATING MONEY TO THIS CAUSE." I could do a whole post about that comic and the response it got.
So it might be a bit unfair to use these pages as my reasoning why Batman would never use a gun, and would always find another way to save the day because he's frickin'
Batman. It's a very biased perspective. But in this case, I believe it also entirely fits with Batman as a character, and how he's always reacted to guns and gun violence.

WARNING: this is the single most graphic description of exactly how the Waynes died.
( Why Batman will never use a gun... in graphic detail )