Generally speaking, the most appealing cartridges (to me) are the ones I've loaded.
I am a sucker for linked ammo, though, even if it was made in a dismal factory behind the iron curtain.
I also find spent casings attractive. Not sure why that is.
Sometimes it's not the cartridge, but the packaging that makes me drool.
Sometimes it's the scenery.
Other times, it's the quantity, and colorful boxes.
Then again, there's also heritage; handling the works of passed away family members.
Other times it's just for shock and awe.
And sometimes I just like to line them up and admire my handiwork.
But more than anything, I like it when they go "BANG"!!!!