I like some of the racers from this era like the Wedell-Williams, Travel Air Mystery Ship and Laird Super Solution. I also like Schneider Cup racers like the Curtis RC3 and equivalent Supermarine's. Those designs, engines and fuel technology contributed much to WWII aviation.
Then there's the P-26, F4B/P-12 and P-6. The F9C, F3F, O2U, ALL of the Consolidated flying boats, the Martin M-130 Clipper and ALL of the Sikorsky flying boats. For some reason I'm not that crazy about the Boeing 314. The longer I sit here the more that come floating into my brain. I have a definate bias towards the US designs, the Navy, and the flying boats. And I'll take Glen Curtis over Orville and Wilbur any day.