Portal
By
lychee — Particle effect based portal | Multi-dimensional tunnels
Tenebris
By
Hafixion — Descend into the underworld with this world generation plugin.
PKAntiCrystal
By
PkDevelopment — PKAntiCrystal is a lightweight and easy-to-use Minecraft plugin that disables crystals on the server
No Physics
By
jojodmo — Extremely lightweight, easy to use plugin that disables physics in regions, per-world, or globally