Hat tip to Tam, but with a twist (I'll list what I think is the practical alternative).
Broomhandle Mauser. Impossible to conceal carry but oozes sophistication and history, possibly the coolest "steampunk" pistol of all time. Practical alternative, the classic 9x19 Luger.
Walther PPK. Easy to conceal carry, but expensive tiny bullets. If James Bond didn't carry one there wouldn't any appeal at all. Practical alternative, 9x18 Makarov
44 AutoMag. It's revolver only hunting in some GMU's in my state. Reloader only proposition. No practical reason to own one, but oh so cool. Used in Mack Bolan novels. Practical Alternative, A 44 Rem Mag hunting revolver by Ruger or Charter Arms.
Desert Eagle in 357, 44 Mag, or 50 AE. The gas system fouls quickly, they are heavy as sin, not concealable at all. Also used in Mack Bolan novels. Practical alternative, 1911 in 45 ACP with a 400 Corbon barrel and spring.
Comments are open for any additions to the list.