Just a few off the top of my head
WWI:
Sopwith Camel, Fokker D.VII, Spad 13, Nieuport 17
Interwar:
Hawker Fury, Supermarine S.6
WWII:
Avro Lancaster, Hawker Hurricane, DC-3, B-29, P-51 Mustang, BF-109, P-40 Warhawk, DeHavilland Mosquito, Spitfire
Cold War: (1950-1990)
F-86 Sabre, MiG-15, F-4 Phantom, MiG-21, Dassault Mirage III, EE Lightning, EE Canberra, U-2, SR-71Blackbird, F-104 Starfighter, B-52 Stratofortress, Tupolev Tu-95 Bear, F-14 Tomcat, UH-1 Huey, Harrier,
Post Cold War: (1990- ) Most of these started service before 1990, but I consider them moden as they are still going strong today.
F-16 Viper, F-15 Eagle, Sukhoi Su-27 Flanker, Mil Mi-24 Hind,
Timeless icons: More representative of accomplishments than eras
Boeing 707 (Truly brough air travel to the masses)
Concord (To think it could exist in the civilian world!)
C-130 Hercules (When the last Raptor goes to the boneyard, the pilot will be flown home in a Herc!),
Cessna 172 (How many pilots got their first taste of flight in one?)
DeHavilland DHC-2 Beaver (The stuff of bush flying legends)
NA Texan/Harvard (No explanation required!)
Of course, it’s all very subjective and open to debate.