Refer to username.
I have a few quirks. I'm a rather quirky guy, after all.
We'll start with the obvious.
Wrist-wrenching, face-slapping, palm-stinging, bench-clearing
RECOIL! I am shamelessly addicted to thumpers. Examples: The Monster, various S.A.S.S. conversion kits, AMT .50 A.E.-cal'd Automag V, .44 Mountain Gun.
Oddnesses. The odder the better. Typified by the "What the HECK are you shooting?" inquiry. Super-thumpers tie into this bit as head-turners also. Examples: Astra 600, Steyr-Hahn 1912, Broomhandle Mauser, The Monster, AMT .30 Carbine-cal'd Automag III.
BIG bores. Examples: .45-70 Trapdoor Springfield, Automag V, Webleys, 1917s, ADC .45 ACP M-1 derringer, Shansei Arsenal .45 ACP Broomhandle Mauser, .358 Winchester S.A.S.S. conversion kit.
Cool calibers. Examples: Glock 32, CZ-52, Automag III and V, .44 Mountain Gun, .400 Cor-bon 1911 barrel, Remington M-81 in .35 Remington.
Classics/Antiques. Typified by Blued Steel and Polished Walnut. Embodying Style, Character, History, and Panache. Examples: Trapdoor Springfield, Colt Lightning Rifles, Webleys, 1917's, Colt 1903, Broomhandle Mausers, Police Positive Special, Remington M-81's, Swedish Mauser, Mannlicher-stocked Mexican Mauser, Parker 10ga. SXS hammer shotgun, Winchester M-'97 shotgun.
I like my quirks. Lots of overlap in the collection, which makes for liking a given gun for LOTS of reasons.