There's a few games that don't have galleries for animated/video segments, and only have a CG gallery or nothing at all. Is there a tool to be able to extract this content from the game's files?
Yes,
GAME RIPPER can extract videos from Ren'Py as well as from Unity games.
By default GR will only show gallery for CG, animations and H scenes, but if you check the "Unpack and exit" checkbox (or run with the "gameripper.exe -d" flag), then it will extract
all files, even the ones not recognized by GR and not shown on the interface (these include videos). I have tested it with KrKr3, Godot, Ren'Py, WolfRPG, RPG Maker, Unity engines with videos in Animated GIF, OGG Theora, MPEG1, MPEG4 and WebM formats. Other formats should work as well.