Randomized Map-specific Ores
Piezo_

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

golden lava
GigaByte

add golden lava

Sticks Stones
MikeRedwood

Makes Sticks from leaves and scatters small stones

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

Beautiful Boulders
regulus

Procedurally Generated Rocks with (pretty) Accurate Collision Boxes

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.

Trucraft
mt-mods

An alternative crafting system done entirely in the world.

Underground Survival Lighting
Arkatron

If you like underground light in survival, use this mod, it can help that.

Floof
Momo

Add BicBiomeCraft inspired biomes, tools, and items.

A Cute Flower
lml55

Adds an innocent flower with some head armor

World Borders
argyle

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

Obdy
Sires

Adds some pretty OP tools :)

Spawn redo
cathaya7d4

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

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.