My second time through on New Vegas and I my character is the opposite of the do-gooder I played in the first go round. So, when I encounter the Lonesome Drifter on my way to Vegas I killed him in coldblood . . . naturally.

I was quite surprised when I entered the Tops Casino (having left my companions outside) and discovered that the Mysterious Magnum is automatically a holdout weapon! Awesome! So, at level 6 I decided a change in battle plans was in order . . . I died a few times, but with the Mysterious Magnum in hand I was able to kill everyone at the Tops starting with Benny. (Sneak attack critical with the Mysterious magnum and he is dead in two head shots.)

Now I'm at level 16 and I still use it regularly - this item is just plain fun. The best holdout (gun) weapon as far as I know with its own cool special effects sounds. :celebration:

I agree that it is the best holdout weapon.
Also, you can get it by playing nice.

And it plays the music whenever you draw or holster it.

Well you just closed off a few quests, congrats.