Deprecated and replaced by a new mod Vehicle -_- RTS Controls https://mods.factorio.com/mod/vehicle-_-rts-control
Providing the player with new tools or adjusting the game interface, without fundamentally changing gameplay.
Transportation of the player, be it vehicles or teleporters.
Augmented or new ways of transporting materials - belts, inserters, pipes!
New ways to deal with enemies, be it attack or defense.
Armors or armor equipment.