Here's a daft fun vote. Feel free to fight it out in the comments haha

No sound beyond the recorded audio.

I dont think adding a sound effect is always necessary but sometimes it is just for a bit of fun.

https://umd.net/profile/i/thegungetankmaker/section/videos/video/just-a-bit-of-fun-sound-on

I think it totally depends on the style of Gunging if I'm honest.

Certain sound effects we remember and relate link to gungings before. The Klaxon being so identifiable with a tank drop. Toilet flushes and fart noises with more slapstick style kids tv.

I'd say anything more "child like" the gunging/sliming/mess is looking like and themed like (which includes the attire, the setting etc) then the more silly the noises become