InvManager
IlzumiZeminori

Allows to check and remove items from players' inventories

Inventory Overflow
monk

If main is full, place nodes into the next available inventory

Kill Button
niwla23

Allows you to kill yourself from the UI

Complete and Total Lua-Only Inventory Rewrite
Noodlemire

Creates a completely custom inventory system, which doesn't rely at all on any of the usual UserData objects.

Beamer
Clyde

Beam items or nodes from your inventory to the inventory of your friend.

Sway
lazerbeak12345

A simple inventory that makes use of Flow forms.