The only 'pusher' aircraft I know of that has been used in active military service is the SAAB 21. There are several prototypes out there, but I can't see that any others were used.
Which, if any, other aircraft are there? Maybe the Japanese 'shinden' but if memory serves me that is only a prototype.
If you also count drones, the General Atomics MQ-9 Reaper Drone is a pusher propeller aircraft in active service.
Here are some others:
You may notice that a lot of these aircraft are very old designs. The problem is in 1914 the US Army (there was no US Air Force yet) banned pusher type aircraft after a number of pilots died in them. This mentality carried over on the other side "of the pond" and very few pusher type aircraft entered service after 1916. The SAAB 21 was responsible for the development of ejection seats because a major problem with bailing out was hitting the propeller. Because the prop was behind the pilot, bailing out meant getting pushed through the wood chipper...
The B-36 is a good example of this configuration in its limits. It is a massive aircraft with a 19 foot propeller (second largest propellers in use). Engine fires were common due to mounting the engines backwards and not getting sufficient heat over the carburetors. The aircraft was later modified as the XB-60 with swept wings and 8 jet engines but was inferior to the Boeing XB-52 (later becoming the B-52) and was abandoned.
The other problem is that a pusher type design contributes a lot to the drag of the aircraft and is relatively inefficient compared to tractor designs. By the time swept wings were in fashion (mostly because jet engines pushed speeds higher and higher), the need for propeller driven military aircraft dropped dramatically in the jet age.
The German Do335 'Pfeil' was a twin-engined fighter of the forties. One engine driving a tractor prop at the front, and the other driving a pusher prop at the tail, with a long transmission shaft.
The Cessna O-2 (337) quickly comes to mind.
Then there are various UAVs, the MQ-1 and MQ-9 are the most prominent.
And the Convair B-36 is another good one.
The Dornier Do. 335 heavy fighter.
The Kyushu J7W1.
Here are some more pusher types to add to the list. I tried to ensure that all had some kind of active service record, not including evaluation prototypes or designs not built. With a couple of exceptions noted below, all of these served in the First World War.
Fighters and bombers with single pusher propellers: Farman MF.7 and MF.11; Breguet Bre.4 and Bre.5
AGO C.II reconnaissance aircraft, single pusher propeller.
Various German bombers, each with two pusher propellers: Friedrichshafen G.II and G.III; Gotha G.II, G.III, G.IV, and G.V; Rumpler G.I, G.II and G.III; and Albatross G.III.
Flying boats with single pusher propeller: AD Flying Boat; Aeromarine 40; Curtiss Model F; Hansa-Brandenburg CC and W.18; Lohner L; Macchi M.3 and M.5; Grigorovich M-5 and M-9; Beriev MBR-2; and Supermarine Walrus. (The last two were operational in the Second World War.)
Grigorovich M-16 reconnaissance floatplane, single pusher propeller.
There were also a number of aircraft that had both tractor and pusher propellers, such as the Caproni Ca.4 bomber (two tractor propellers and one pusher propeller) and the Zeppelin-Staaken R.VI bomber (two tractor propellers and two pusher propellers).
