I am not a dog trainer and I can not say that my dogs are perfectly well behaved, but here are a couple of commands that I think all dogs should be taught no matter what.
1) DROP IT. I have taught this to my dogs from day one. Some came to me as a puppy and some were older so this is not just for the young ones...its for all dogs. I can not tell you how many times a dog got something in their mouth that was potentially dangerous and the need for them to release it immediately very necessary. To have a dog 'drop it' on command is vital. You can say it when they pick up your shoe, a dead animal, feces, food items that are dangerous to dogs (ie, onions, mushrooms, chocolate, etc) or you simply want to play fetch not tug.
2) COME. As humans we are terrible at consistent commands. We teach this command but will use 'come' for bad times and then they don't always listen. Remember: if you give the command to 'come' and they are punished for being bad...you have taught them that 'come' is not always a positive experience. Problem really lies in the time you need them to 'come' and they don't. You may need them to get back in your control because you see another dog, a hazard, dropped the leash, need to hurry, etc. If they know that 'come' is an order to listen to because punishment doesn't follow, you will be able to use the command when its needed most and possibly ensure a better day at that point.
3) ENOUGH (or whatever word you wish to use). Doesn't matter if Fido is a miniature Poodle or a large German Shepard barking needs to be under your control. Its great that dogs bark when someone enters your property or knocks on the door, but that barking needs to have a clear end. A command like 'enough' allows you to acknowledge the signaling of a breech in security, but once you have checked the situation and all is clear...so no more barking. Yappy dogs or barking dogs are a product of your doing...not the dogs. Excessive barking is often a product of ignoring their communication or rewarding them for barking...so consider this new command for your own pup.
These commands for the most part are there to make sure you can keep your pup(s) safe and your home a happy one.