Draconis
ElCeejo

Adds advanced Dragons and powerful equipment.

Nether
PilzAdam

Adds a deep underground realm with different mapgen that you can reach with obsidian portals.

Mineclone2 New Ores and Deepslate
NO11

Adds 30 new deepslate blocks!

Randomizer
NO11

A survival challenge. Try to survive in a randomized world.

Native Villages
Liil

Adds villages of native people to the world.

Alien Material
debiankaios

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

Multiple Biome Generator
chaosomnium

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

Skygrid
ROllerozxa

Custom skygrid mapgen.

Mineclone2 Nether Gold Ore
NO11

Adds Nether Gold Ore

Dense Ores
benedict424

Adds rare ores with twice the drops of their normal counterpart.

Base Modpack
karlexceed

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

Grave
ElCeejo

Adds an eerie biome with multiple mobs.

Mineclone2 Underwater Challenge
NO11

A survival challenge for Mineclone2. Try to survive in a flooded world.

Nodecore Skyblock Ultra Hardcore
Kimapr

The ultimate skyblock challenge

NodeCore Lignite
Winter94

Adds Lignite, an ore of coal.

Trucraft
PolySaken

An alternative crafting system done entirely in the world.

Kitty/Kitto Ores
nemokitty9

Nemokitty9's own ore pack. Includes Tools!

Sailing
cakenggt

Live in a tropical paradise where you can sail, mine coconuts, etc.

Underground Challenge
Hume2

Explore all 62 underground biomes!