Can’t think of a corny German song right now 
Even though this song by Thomas D. is called “Liebesbrief” ( love letter ) I wouldn’t call the song a “Schnulze”…judge for yourself:
My favorite English “Schnulze” is this one 
…closely followed by
…do you have a favorite “Schnulze”? Confessions ( Geständnisse ) are welcome 
One of my favourites is “Deine Spuren im Sand”, because we always said: “Deine Spuren im Sand, die eine, das ist meine und die Schleifspur, das ist Deine…”
Deine Spuren im Sand: Howard Karpfenquäl
That’s great 
…den ( Witz ) kannte ich noch nicht. Thanks for the link, but I remember the song and I don’t think I can get myself to listen to it again