Pretty straight forward this one. If it flew between August 1914 and November 1918 and had a single seat in any scale it’s in.
list of types: ( far from comprehensive)
Britain:
Bristol Scout
Sopwith Pup, Camel, Comic, Dolphin, Snipe.
De Havilland DH1, DH2, DH5/5a
RAF Se5a
Belgium:
Hanriot HDI
France:
Nieuport 11, 17
SPAD VII, X, XII
Austria Hungary:
Phoenix DI
Oeffag Albatros DIII
Germany: