Banker / Minter

bank / banco / banque

Will direct the banker to open your bank box.

balance / statement / solde / saldo

Will cause the banker to tell you the amount of gold in your bank box (excluding bank checks)

check (amount)

Will command the banker to issue a bank check in the indicated amount (5,000 to 1,000,000 gold)

withdraw (amount)

Will command the banker to add the indicated amount of gold to your backpack.

Barkeep / Towncrier

News

The barkeep will give a scenario hint, just like a town crier.
See the compendium article on Barkeeps on how to setup rumors.

NPC / Vendors / Guildmasters

(name) buy

Will show you any goods the vendor has for sale.

(name) sell

Will present you with a list of items you are carrying that the vendor will purchase.

(name) join

Can be used with NPC guildmasters. They will respond with the amount of money you have to pay them to join that guild. Right after that just drop the money on the NPC to join.

(name) quit / (vendor name) resign

Can be used with NPC guildmasters. This will remove you from an NPC guild.

(name) time

The NPC will give you the current server time.

(name) move

The NPC will move to a nearby tile.

(name) train

The NPC will provide you with a list of skills that they can train you in.
If you cannot learn anything additional in this skill, or do not meet the requirements the skill will not be listed.

(name) train (skill)

The NPC will indicate the amount of gold they can accept to train you in the indicated skill.

Stablemaster / Animal Trainer

Retrieve / Claim

Will claim all of the pet(s) the stablemaster has stabled with him.

Retrieve (pet name)/ Claim (pet name)

Will retrieve the specific pet from the stablemaster.

Claim List

Will show you a list of the pets you currently have stabled.

Stable / Stall

Will give you a target cursor allowing you to stable a pet.