Fancy Vend
ChimneySwift

A full-featured, fully-integrated vendor mod for Minetest

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.

You Can't Touch It Either
Avicennia_g

Simple mod adding lockable storage shelves to Nodecore.