Adding a relatively new feature to MMORPGs would be allowing players to mount objects.Horses and other mounts already offer players an ability to travel further and faster so why not expand upon it?



Weapons:
Siege Weapons
Mangonels,ballistae,catapults,trebuchets,magical equipment etc

Such weapons can be attached to beasts of burden to be transported rapidly and once were needed unloaded and activated by mounting.I think a FPS system could work best.Possibly require some form of ammunication cart.

The weapons can also be fitted to the larger city walls and be PC/NPC controlled.



Ship Weapons
Greek fire style torches,catapults,ballistae etc

When a ship is crafted it can be designed to offer different 'turrets' depending on class of ship and miney and effort that is going to go into its creation.Once fitted a player can walk around on its deck as normal boarding enemies and making use of their own arsenals.However the player would also have the option to mount turrets and use them instead.Ammunition would be taken directly from ship hold.



Beast Weapons/Mountings
Similar to a normal mount some greater beasts are ridable,the difference being they are also minature weapons platforms.Some giant beasts could allow a position for a few ranged units as well as the beast master.Other lumbering brutes could be so large as to allow siege sized weapons to be mounted.These operate as the 'turrets' of a ship.


All of the above shouldn't appear until the game has progressed quite a distance as they would be very powerful.That is not to say they are not available,simply that the materials,price and effort to create them would not exist.These are also major guild items and thus would be seen in guild rivalry,to prevent simply using them for questing.Possible make them have a huge upkeep while operating making them uneconomically viable to quest with and would be reserved for us only in the direst of times.



Tools
Mountable objects for crafters/resource collectors:

Steam drills,mine carts,dwarven constructs,sawmills(as oppsed to put tree in one side and get plank out of other),windmills etc.

Use of mounted beasts to pull carts etc.

Haha, mountable positions. Classic.

Heheh oops should have noticed that.

Just some other interesting options:

Carriages/transport to bring players around(not a fan of the teleport/instant transport as it significantly reduces the size of the game world).A player goes to a stables and selects to take a scheduled carriage/transport to another town.These could be easily player run,either by playing personally driving the carriage or by players employing NPCs to make the run.The transport route is created by choosing the name of the destination from a list of all other stations and pathing being automatically done along the roads.

A player is then 'postioned' into the transport but can still use all their abilities.So if a highway man did stop their carriage they would be able to defend themself while getting a small defense bonus for being inside vehicle.These transports could also be parts of caravans with players taking different seats on the vehicles for defense.Mainly transports simply allow for faster,safer transport while also allowing for large amounts of cargo.