The Messerschmitt Bf-109 was designed before WW2, and the earliest versions saw combat in the Spanish Civil War. It became the most widely used fighter in the Luftwaffe with 30,000 being produced in many variants and sub-variants.
The 109 was also used by at least ten other countries, but was out-classed by the end of the war, and only lived on as the Avia S-199 and Hispano HA1.112.
The 109F had an improved Daimler Benz engine which meant a new nose design, new semi-elliptical wings, new radiators, new tailplane without struts, and a new rudder. It was armed with 2 x 15mm machine guns and 1 x 15mm cannon (later changed to a 20mm cannon) firing through the propeller. It was initially criticised for being lightly-armed, but the performance and handling were much improved and many Luftwaffe pilots made good use of this.
This example is a Bf-109-F2 of JG53, circa 1941.