I can't articulate why, exactly, but I've always loved the PBY Catalina, a flying boat built in the years leading up to WWII. It's ugly and slow, but it's also amphibious and looks like a hell of a good time.
Functional Catalinas are assuredly multi-million-dollar machines. Odds are really good that I'll never get to fly one. Bummer.
That's because they are dead sexy, you have no choice but to instantly fall in love with them.
Just! So! Utilitarian!
If you like the Catalina you might also check out the Grumman Albatross. It's a similar plane but looks slightly more utilitarian. Anyway, Jimmy Buffet has one and writes about it extensively in his books (Specifically "A Pirate Looks at Fifty). You can see his plane here:
http://www.buffettworld.com/airplanes_albatross.html
Although, I believe those pics are a bit old. If I recall correctly his Albatross has been converted to turbo props.
truesus-
When I read through your comment, my first thought was that the big radial engines are what make these big old seaplanes so special. Turbines are nice, and all that, but they just don't have hundreds of pistons and valves trying their damndest to fly out of the crankcase at every moment. For the same reason that reciprocating engines are far more unreliable, I think they're just that more interesting.
But, the Albatross and the similar Canadair CL-215 are both damned amusing planes.
--Dan