This is a (hopefully) complete list of the anti-aircraft guns used by the Wehrmacht, compiled by Antonio Pena with additional info from the other members of the forum.

German Weapons
2.0 cm Flak 28 and 29 (Designed by Oerlikon and purchased prior to the outbreak of war, many others adquired from Czechoslovaquia, France, but without Fremdegerät number asignation)
2.0 cm Flak 30 (Adopted in 1935 as main light Flak gun, and remained in service throghout the war)
2.0 cm Flak 38 (Developed by Mauser as a replacement for the Flak 30. In service from 1940. Nearly 18.000 made)
2.0 cm Gebirgsflak 38 (The same weapon as above, with a lightweight carriage for mountain use)
2.0 cm Flakvierling 38 (Four Flak 38 barrels together in a special carriage (Sonderanhänger 52). The most effective light AA gun)
3.0 cm Flak 103/38 (A makeshift weapon. Marriage between the Aircraft Mk 103 Kanone and the Flak 38 Mount)
3.0 cm Flakvierling 103/38 (Four Flak 103/38 barrels in the Flakvierling 38 carriage)
3.7 cm Flak 18 (Developed by Rheinmetall, little more than a enlarged version of the Flak 30. Production stopped 1936)
3.7 cm Flak 36 (Redesigned Flak 18 with a new lightweight 2 wheel carriage)
3.7 cm Flak 37 (Same gun as above, but with the Flakvisier 37)
3.7 cm Flak 42 (Originally designed for naval use, but many used as coastal gun)
3.7 cm Flak 43 (Designed with a new gas-operated breech)
3.7 cm Flakzwilling 43 (Twin barrelled version of the Flak 43)
3.7 cm Gerät 339 (Krupp project for the Flak 43 programm, not accepted)
5.0 cm Flak 41 (Designed by Rheinmetall. Nearly 200 made in 1940, but shortly after take out of service)
5.0 cm Flak 214 (Former Mk 214 A aircraft cannon mounted in Gerät 58 carriages)
5.0 cm Gerät 56 V1a, Gerät 56 G, Gerät 56 K and Gerät 56 M (Prototypes only.)
5.5 cm Gerät 58 (Rheinmetall design for a weapon systemwith radar and firecontrol equipment, not completed before war ends)
5.5 cm Gerät 58 K (Krupp design for the same specification of above)
7.5 cm Flak L/59 (Designed by Rheinmetall but not accepted for service)
7.5 cm Flak L/60 (Designed by Krupp not adopted by Germany but exported, many guns taken after the outbreak of war)
8.8 cm Flak 18 (First of a serie that become the most known antiaircraft and antitank gun of the war)
8.8 cm Flak 36 (Redesign of the Flak 18 with minor ghanges in carriage and barrel made in three sections instead of one)
8.8 cm Flak 37 (Improvements in the data transmision system and a new barrel in two sections)
8.8 cm Flak 37/41 (Flak 41 barrel on the Flak 37 carriage)
8.8 cm Flak 36/43 (Flak 41 barrel on the Flak 36 carriage)
8.8 cm Flak 39/41 (Flak 41 barrel on the 10.5 cm Flak 39 carriage)
8.8 cm Flak 41 (New design by Rheinmetall, the gun was mounted in a turntable, with great improvements in ballistics, a powered loading mechanism and a three sections barrel in the first guns produced and a two sections in the latest)
8.8 cm Gerät 42 (Krupp design for the same specification of the Flak 41, not accepted for service)
10.5 cm Flak 38 (Designed by Rheinmetall as a full power operation gun, with a high rate of fire)
10.5 cm Flak 39 (Redesign of the Flak 38, changing the electric power supply from direct to alternate, new barrel in five sections instead of one of the Flak 38, and a new data transmision system)
10.5 cm Flak 39/40 (A Flak 39 gun in the platform of the 12.8 cm Flak 40, never reached production)
12.8 cm Flak 40 (The most powerfull antiaircraft gun produced, originally as a mobile gun but the majority used in static emplacements)
12.8 cm Flakzwilling 40 (Two 12.8 cm Flak 40 putted together to arm the Flaktowers erected in many German cities in place of the proposed 15 cm antiaircraft guns designed for them. About 34 produced)
12.8 cm Flak 45 (Redesign of the Flak 40, with larger chamber and a longer barrel and a muzzle brake.Only one prototype produced before the war end)
15.0 cm Gerät 50 (Flak Projected by Krupp to a 1936 requirement of the OKL. Dropped in 1940.)
15.0 cm Gerät 55 (Flak Projected by Rheinmetall to a 1936 requirement of the OKL. Dropped in 1940)
15.0 cm Gerät 60 and 60F (Flak Design made by Krupp, after discarding the Gerät 50. (F means fest, static))
15.0 cm Gerät 65 and 65F (Flak Design made by Rheinmetall, after discarding the Gerät 55. (F means fest, static))
24.0 cm Gerät 80 (Krupp project combining a Luftwaffe gun with a Navy carriage, cancelled in 1943)
24.0 cm Gerät 85 (Rheinmetall project combining a Luftwaffe gun with a Navy carriage, cancelled in 1943)

Captured Weapons
2.0 cm Flak Madsen (Original Madsen M33 and M35, captured to Czech, Polish,Norwegian, Belgian and French armies)
2.0 cm Flak 282 (i) (Ex-italian Breda M-35, used in North Africa and after Italian surrender)
2.0 cm Flak Scotti (i) (ex-italian Scotti da 20/77, only limited use by German Army)
2.5 cm Flak Hotchkiss (Ex-french Mle 38 and Mle 39 Hotchkiss AA guns)
3.7 cm Flak Breda (i) (Ex-italian Breda M39)
3.7 cm Flak 39a (r) (Ex-russian M-39)
4.0 cm Flak 28 (p) (h) (e) and (n) (Ex-polish, dutch, british and norwegian 4.0 cm Bofors.)
4.7 cm Flak 36 (t) (Ex-czech M-37, only small numbers in service)
7.5 cm Flak M-17/34 (f) (Ex-french Canon de 75 Contre aeronefs Schneider)
7.5 cm Flak (b) (Ex-belgian Canon de 75 FRC Mle 27)
7.5 cm Flak M 30 (f) (Ex-french Canon mle 30)
7.5 cm Flak M 33 (f) (Ex-french Canon mle 33)
7.5 cm Flak M 36 (f) (Ex-french Canon mle 36)
7.5 cm Flak M 35 (h) and (d) (Ex-dutch and ex-danish Vickers M 35 guns)
7.5 cm Flak Vickers (e) (Ex-british QF, 3 in, 20 cwt, many captured in France from BEF)
7.5 cm Flak M37 (t) (Ex-Czech 7.5 cm Vz37, delivered in 1939 to Italy but after Italian surrender in service for German troops)
7.5 cm Flak 264/3 (i) (Ex-italian Canone da 75/46 M 34, the standard AA gun of the Italian Army)
7.5 cm Flak 264/4 (i) (Ex-italian Canone da 75/46 M 40, the same gun as above but for static use only)
7.62 cm Flak 266/1 (i) (Ex-italian Canone da 76/40 CA, a dual purpose AA/coastal gun used from WW 1)
7.62 cm Flak 266/2 (i) (Ex-italian Canone da 76/40 modificato 35, modernised version of the Flak 266/1)
7.62 cm Flak 266/3 (i) (Ex-italian Canone da 76/45 CA, another modernization of the Flak 266/1, with a longer barrel)
7.62 cm Flak M 31 (r) (Ex-russian M 31, the first modern heavy AA gun, many later rebored to 8,8 cm)
7.62 cm Flak M38 (r) (Ex-russian M38, a version of the M 31 with a two axle carriage, also many rebored to 8,8 cm)
7.65 cm Flak 33 (t) (Ex-czech 8 cm Vz33, the standard Czech AA gun)
7.65 cm Flak 37 (t) (Ex-czech 8 cm Vz37, a modernized version of the M 33 with a longer barrel)
8.35 cm Flak 22 (t) (Ex-czech 8,35 cm Vz37, many also captured in Yugoslavia)
8.5 cm Flak (r) (Ex-russian M 39, the best heavy AA gun in russian service, many later rebored to 8,8 cm)
9.0 cm Flak M 39 (f) (Ex-french Canon de 90 mm DCA Mle 26 the heaviest AA gun in french service)
9.0 cm Flak M 12 (t) (Ex-czech 9 cm Vz 12/20, captured after czech takeover and also from Russia and Yugoslavia)
9.0 cm Flak M 41 (i) and 309/1 (i) (Ex-italian Canone da 90/53 CA, the best Italian heavy AA gun)
9.4 cm Flak Vickers M39 (e) (Ex-british QF, 3.7 in, the standard heavy AA gun many captured from BEF)
10.2 cm Flak (i) (Ex-italian Canone da 102/35, dual purpose AA/coastal gun only 4 in German service after Italian surrender)

Flak: Flugabwehrkanone (antiaircraft gun)