This is a (hopefully) complete list of weapons designed originally for Shipboard or Coastal defence used by the Wehrmacht, compiled by Antonio Pena with additional info from the other members of the forum.
The list includes the weapons designed originally for Shipboard or Coastal defence, made in Germany or captured. The coastal front between the French-Spanish border and the Norway-Finnish border was defended mainly with captured weapons, but the most important part of the pieces were not designed originally for that purpose.

A complete list of the weapons used to defend the "Festung Europe", will include nearly all the guns made in Europe from 1870 onwards, and are outside of the scope of this list, many of them are described under the chapters of Light and Medium, Heavy, Railway and Fortress artillery.

German Weapons
3.7 cm Schiffskanone C/30 in Einheitslafette C/34 (A naval pattern dual purpose antiaircraft-coast defence gun, single or twin mounts.)
7.5 cm Panzerabwehrkanone 40 in Marinelafette 39/43 (A standard PAK 40 in a naval pedestal mounting, employed also as shipboard gun. Only due to the Mounting this gun is here)
8.8 cm Schiffskanone C/35 in Unterseebootslafette C/35 (A naval design , small number installed in casemate mountings)
10.5 cm Schiffskanone C/32 in 8.8 cm Marine pivot lafette C/30D (Originally a shipboard antiaircraft/surface gun)
10.5 cm Schiffskanone L/60 in Einheitslafette (A dual purpose antiaircraft/coastal gun, developed from the 10.5 cm Flak 38)
12.8 cm Schiffskanone C/40 in 12.8 cm Dopellafette (PzK) C/40 (Projected coastal version of the 12.8 cm Flak 40)
14.0 cm Schiffskanone L/56 mit Ladeeinrichtung auf 15 cm TorpedobootsKanone c/36 (Originally designed as naval gun for the Yugoslavian Navy, Only one prototype)
15.0 cm Schiffskanone C/28 in Kusten Marine pivot lafette C/36 (A naval gun with purpose-designed coast defence monting)
15.0 cm Schiffskanone C/28M (The same gun fitted into a mobile mounting)
15.0 cm Schiffskanone C/28 in Zwillingslafette (The same gun as above in a barbette type double mounting)
15.0 cm Schiffskanone C/28 in Kusten Dreiheitslafette LM 43 (The same gun as above mounted in a armoured barbette mounting)
15.0 cm Torpedobootskanone C/36 (An old torpedo-boat gun usually mounted on the original turret)
15 cm Schiffskanone L/36d
15.0 cm Schiffskanone L/40 (Old WW 1 coast defence gun usually mounted in concrete casemates)
15.0 cm Schiffskanone L/40 (Old WW 1 shipboard gun, used for coastal defence after 1939)
15.0 cm Unterseeboots und Torpedoboots Kanone L/45 (An ex-naval shipboard dual purpose gun of very modern design)
17.0 cm Schiffskanone L/40 (An old shipboard gun used for coastal defence, and as railway gun)
20.3 cm Schiffskanone C/34 (An ex-naval weapon designed for the "Blücher Class" cruisers, usually mounted on turret)
24.0 cm Schiffskanone in Drehschiesslafette C/98 (An old naval gun usually mounted on a barbette carriage or in single turrets)
24.0 cm Schiffskanone L/35 (Ex-naval gun designed before WW 1, and adapted for coastal defence)
24.0 cm Schiffskanone L/50 (Ex-russian guns captured in 1915, after WW 1 installed in Borkum)
28.0 cm Schiffskanone L/40 (Ex-naval gun designed for the "Deutschland class" battleships)
28.0 cm Schiffskanone L/45 (Old "Nassau class" dreadnoughts guns)
28.0 cm Schiffskanone L/50 (Old "Moltke class" battlecruisers guns)
28.0 cm Schnellade-Kanone C/34 in Drehschiesslafette C/28 (Main turrets of the battlecruiser "Gneisenau", converted to coastal defence in Norway)
28.0 cm Kusten Haubitze (An old design, similar to the 28.0 cm H L/12)
30.5 cm Schiffskanone L/50 (Old "Derfflinger class" guns, built by Krupp and Skoda)
38.0 cm Schiffskanone C/34 (Gun designed originally for the "Bismarck class" battleships, 4 at Oxsby (Denmark), 4 guns at Hanstead and 3 at Kristiansund (Norway), 4 at Haringzelle (France))
40.6 cm Schiffskanone C/34 in Schiessgerät C/39 (Originally designed for the "H class" battleships, 3 guns in Sangatte (France), 4 at Trondenes and 3 at Engeløy (Norway))

Captured Weapons
9.5 cm Küstenkanone (f) (Ex-french canon de cote de 95 M 93) (Only used in France)
12.2 cm Küstenkanone 393 (r) (ex-russian coastal gun M ?)
15.2 cm Küstenkanone 456 (r) (ex-russian coastal gun M 04)
15.5 cm Küstenkanone 418 (f) (ex-french Canon de 155 GPF captured near Reims)
20.3 cm Küstenkanone L/45 (r) (old russian coastal guns from Sevastopol )
24.0 cm Schnellfeuerkanone C/97 (h) in Drehschiesslafette C/97 (h) (Naval guns from two Dutch coastal defence ships)
25.4 cm Küstenkanone 572 (r) (ex-russian coastal gun M 10)
27.0 cm Küstenmörser 585 (f) (ex-french coastal howitzer M 89)
30.5 cm Küstenkanone 626 (r) (ex-russian gun) (Captured in Narvik, en route from France to Finland, and restored by Krupp)
30.5 cm Haubitze modell 16 (Bofors) (Ex Norwegian?) (4 emplaced in Narvik)
34.0 cm Küstenkanone Modell 12 (f) (ex-french coastal gun M 12)

The following guns are of Norwegian origin and only used in Norway:
10.0 cm SKL40 MII Bofors (Removed from Norwegian ship "Æger") (German name: 10.0cm SKL 40(n))
10.0 cm L/40 MI (from the Norwegian ship Fröya)
12.0 cm L/40 Schneider
12.0 cm L/44 Armstrong (from the N. ships Tordenskiold & Harald Haarfagre)
15.0 cm L50 Bofors. German name:15.0 cm SKL 50(n)
15.0 cm L47,5 Armstrong. German name:15.0 cm SKL 47,5(n)
21.0 cm L45 St-Chamond. German name:21.0 cm SKL 45(n)
24.0 cm St-Chamond. German name:24.0 cm HL/12,7(n)
28.0 cm L40 Krupp (the guns which sunk Blücher) (German name: 28.0 cm SKL 40)