Water Life
Gundul

new mobs for your river and sea water

Draconis
ElCeejo

Adds Dragons and related resources and equipment to Minetest Game

Technic
RealBadAngel

Extensive machinery mod with electricity and ores.

Ethereal NG
TenPlus1

Ethereal mod uses the v7 mapgen to add many new biomes to the world.

Alien Material
debiankaios

Adds new blocks, items, and tools from aliens. A new time begins.

Caverealms Lite
Shara

A mod for Minetest to add underground realms.

Cloud Items
Panquesito7

Powerful cloud tools.

Technic Plus
mt-mods

Technic fork with focus on features and stability

Multiple Biome Generator
chaosomnium

230 Pseudorandomly Generated Biomes, Trees, Fruits, Ores, Tools, and Liquids

Base Modpack
karlexceed

This combines several other mods that I consider a basic minimum starting point for worlds.

Zero-Effort Custom Minerals
Piezo_

A tool for registering entire materials, complete with ore generation, tool-sets and automatically generated sprites with almost no effort required

Melterns
IcyDiamond

Tinkers Construct in Minetest!

Kitty/Kitto Ores
nemokitty9

Nemokitty9's own ore pack. Includes Tools!

Trucraft
PolySaken

An alternative crafting system done entirely in the world.

Randomized Map-specific Ores
Piezo_

Adds two randomly created ores to each world with varying properties depending on the world's seed

Obdy
Sires

Adds some pretty OP tools :)