Dirt Tunneler
Neuromancer

Makes dirt deeper and you can tunnel through it just by walking through it. Press spacebar/shift to tunnel upward/downward with auto placed ladders.

World Borders
argyle

Add impenetrable barriers to the sides and bottom of the world.

A Cute Flower
lml55

Adds an innocent flower with some head armor

New Horizons
Hi_World

Adds 4 new biomes and TONS of new blocks!

Sticks Stones
MikeRedwood

Makes Sticks from leaves and scatters small stones

Trucraft
mt-mods

An alternative crafting system done entirely in the world.

Unstable Caves
M BLOC

Some stones may cave in if punched, making underground expeditions more risky.

Obdy
Sires

Adds some pretty OP tools :)

Spawn redo
cathaya7d4

Drop-in replacement for default/spawn for more third-party biomes

golden lava
GigaByte

add golden lava

Floof
Momo

Add BicBiomeCraft inspired biomes, tools, and items.

Noriel Sylvire's Minerals Core Modpack
Noriel_Sylvire

An API for automatically registering recipes, nodes and ore generation.

Purple ore
X-DE

Adds new purple ore to floating islands and caves from height 200 to 31000.

treasures
ademant

Treasure nodes with useful items

Mud
Blocky Player

Adds stylish mud blocks and even blocks you can walk through. Setup traps, secret rooms and much more!

Silver
Jackknife

adds silver ore and tools

Too many ores
TeufloV

This adds 53 new ores. But most of them are useless.