Air : Wings of Prey (funny title - bad translation I guess) on realistic mode it is really breathtaking + you can fly hurricanes and spitz aswell as me109s+JU87s
Land : Operation Flashpoint Resistance + WWII mods for that realistic infantry experience
Sea : Silent Hunter 4 + Op Monsun and full manual targetting 100% realism, always trying to recreate das boot (succeeding regularly)
anyway, those are my personal favourites
