Definition ripper is a very useful mod when you have a game and want to extract just the basic building blocks out of it, trimming off the gameplay, survival elements and any other fat that'll most likely just slow things down. Take the exported definitions from the mod, put it into an empty game, drag in i3 (or your inventory mod of choice) and WorldEdit and you've gotten yourself a minimal and lightweight creative building experience.
For my usecase, I wanted to basically scoop out all the nodes from Mineclonia to reduce as much overhead caused by the (admittedly rather heavy) game as possible for a very large map of Gothenburg, such that flying around will load mapblocks as quickly as the engine possibly can load them.
Some notes, from when I used it:
This is specific to Mineclonia, but there is a bug in the current version of the game that causes this mod to crash when attempting to rip the redstone dust node due to the nodebox table being malformed. (See #754 for more details and a fix)
If you're ripping the entirety of a large game, you might run up against the Lua locals limit (which is 200). If a tiles table for a node is used more than once, then it will put it in a local variable for reuse. But this becomes quite an issue when ripping a large amount of nodes if it reuses more than 200 tables. Workaround would be to turn all the locals into globals (s/local //g) but the better solution would be reducing the amount of nodes you're exporting, since you most likely are ripping an excessive amount of nodes anyways. This has now been fixed as of release v02664935.
Aliases won't be ripped, which led to my map having cute little "Unknown Node" trees caused by Mineclonia's tree refactor. You'll have to copy any necessary aliases manually, or make sure no aliases from the game are required if you're loading an existing map.