KeyGood idea:

So-so idea:

Do it if you have no other choice:
What is superbursting or ubering?Superbursting which is this,

, or which some people call ubering, is a brief period of time, 8 seconds to be exact, when a medic and his target become invincible. It takes a great deal of charging on the medic's part to build it up, but it is excellent when used properly for leveling out autogun nests and hordes of enemies. These are usually the deciding points of games where there are many engineers or defenders. These are the perfect way to try to destroy obstacles, as the medic's target also gets unlimited ammo, as well as invincibly. It also conveniently douses any flames the target may have. The uberburst is one of the strongest weapons of the game, and here are some tips on who to uberburst.
How to uber Simply click m2 when the little

appears and your bar in the lower right corner is full. You can either save it or use it immediately. You also have to be healing someone to use it. Remember, your target gets unlimited ammo, and invincibility and is still gaining health when you use it. You must still have m1 on the target, and letting go takes the uber off him.
Who to uberRunner
Summary: Ubering him is a good idea usually, especially if it involves breaking through a mass of enemies. Although he is not the best target, it is usually a great to uber him.
Upsides: With 48 damage point blank, he can simply plow through enemies and autoguns. He is the fastest character in the game, so he can attack far ahead, and is able to keep up pace with you. He can also clear the paths for others in a/d control points, like dirtbowl for example. There are certainly betters to uber, like the firebug for example, which we will talk about next, but he is surely a stable target to superburst.
Downsides: He has to be sure to stay with you and not break the medibeam in order to be effective. If he strays and the medibeam breaks, he is in danger, and will no longer have the benefits of the uber. This is one of the main and only problems with ubering him.
Firebug
Summary: Arguably the best subject to uber, he can do tremendous damage to enemy defense and in my opinion, should be the first person to look for when you uber.
Upsides: A firebug with unlimited ammo is indeed one of the most powerful weapons in the game. Now add invincibility to that. A superburst combined with a firebug can wreak havoc with the opponent's autoguns and any defenses lying around. Firstly, the firebug's speed matches that of the medic, so they can always stay together without breaking the medibeam. All the firebug has to do is spread his flame around, and his powerful afterburn will take care of any survivors. The firebug can also use a flare burst, which kind of helps increase its range, but it doesn't do as much damage.
Downsides: Getting close to the opponent is one of key parts to a successful uber, and that is even more important here. The firebug's only liability is its range, so you must get very close in order to unleash the beast. This is perhaps the only downside to the firebug.
Rocketman

Summary: This is also one of the best. One of the main problems with the rocketman is its speed and reloading time. The uber takes care of the reloading part. The rocketman is perfect for long range firing.
Upsides: Each shot does a whopping 55 damage, so two well placed shots could take out an autogun. It also has quite a bit of splash damage, which is another plus when you want to take out a barricade of enemies.
Downsides: The rocketman is extremely slow, and if the medibeam is broken, valuable uber time will be lost. His rocket fire rate is also extremely slow, which can hinder your progress. Be sure to stand back and fire, or advance and fire. Never be retreating when using an uberburst. One way to show that to your patient is by using

or

depending on which way you are going. It can also be hard to aim with the rocketman when standing from afar. This may lead to your uber being wasted while your patient keeps trying to hit a key autogun defending the point.
Heevee

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Summary: Also a pretty good target, but it is sometimes not a good idea to uber him. Even though he has a really high dps, there are some problems to ubering him. It is best to get up close to the place you are laying siege upon and shooting from there.
Upsides: He has a 120 dps so he can quickly dismantle anything in its way. Autogun nests are no problem for this duo. A heavy medic duo is highly regarded as the best partnership. Unfortunately, ubering can be a bit different.
Downsides: He is slow to begin with, and can be slower when firing. That makes it hard to attack retreating heavies and others. This can lead to a lot of bullets and time being wasted. As stated earlier, standing near the point you are trying to cap is usually better idea. Don't try to break down choke points with the heavy, unless absolutely necessary. A runner or pyro does the job much better.
Detonator

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Summary: Meh. There is really no point in ubering a deto. He can only lay one mine at a time and each shot takes precision and timing, which can take a few precious seconds away.
Upsides: There are really no upsides to ubering the deto, except for the fact that he can lay a bunch of stickies down at a time, which when exploded can do massive damage. He has unlimited ammo so he can lay down carpets of stickies that can demolish defenses.
Downsides: There are really no reasons to uber a deto, as he should be able to do fine without you.
Medic
Summary: The medic is one of the weakest characters to use for attacking. 'Nuff said.
Upsides: There really are none.
Downsides: Well, the medic has only 4 damage a shot which is not great for taking out a big muscular minigun wielding monsters of men. It is just a waste of an uber to do it use it on the doc. It is a good trolling method to uber a medic though, I guess.

Constructor
Summary: He is just a nerfed runner in terms of speed and damage. It is okay to uber him; just pretend he is a noob runner.
Upsides: See the runner profile. He is a much more sturdy version of the runner, so in some situations, it may be pretty good to use him.
Downsides: He is a bit slow and his damage is less than that of a runner.
Infiltrator
Summary: I know there is going to be a lot of debate on this one. The infiltrator is one of the most frowned upon classes, and is generally viewed as a beginner class to use. However this quote from Kalir sums it up quite well.
Infiltrators, assuming they know what they're doing, are actually really good superburst targets. That's a rather risky assumption to make though.
Upsides: His revolver does a lot of damage and his stab can be incredibly useful. 28 damage per shot and a one hit KO are weapons not to be laughed at. He has an uncanny ability to take out multiple defenders and can quickly dismantle enemy defenses.
Downsides: Most infiltrators are noobs, and are not capable of using these seemingly easy to use weapons. They prefer to randomly walk around and attempt to stab without timing.

That just wastes the uber. Also,the uber reveals the infiltrator so the element of surprise is gone, which could complicate things.
Rifleman
Summary: Just don't do this unless you need to...
Upsides: He becomes invincible I guess?
Downsides: There are no benefits to ubering him other than the one stated above, and the health regen. His firing rate does not get faster, and he cannot shoot through you, which limits his abilities to attack enemies.
Quote/Curly
Summary: They can be decent to uber. Their knockback can clear the path for your other teammates to use. They can be pretty useful to uber.
Upsides: They have a pretty rapid fire rate if you get close to your opponent and can do a lot of damage with that unlimited ammo the uber provides. Their speed is also pretty high, so if you uber one, you can drive enemies back pretty rapidly.
Downsides: Their weapon's range is surely a problem. It doesn't go to far so you must get close to be able to be effective.
Here is the ranking of who to uber
in my opinion:

/

and the

can go pretty much anywhere, depending on if he knows what he's doing.
Some tips for ubering1. Count out the 8 seconds. The medic is the most important part of the team, and it will do you and your team no good if you perish. When time is almost up, scurry back to your teammates.
2. Try your best to keep your medibeam on your teammate, though breaking it is not instant death.
3. Using an uber will make someone drop the intel, and you will not count on capture points (someone correct me if I am wrong

) so uber according to the situation.
4. Sometimes, ubers can be used to protect yourself if you are in danger of dying. Not all ubers have to be offensive, after all. "Pop it, don't drop it"-Imp
5. Uber juggling heevees and rocketmen are the best, since they have slow reload times.
Will add more later
Uber JugglingWhat is this? Well, since your uber replenishes the ammo of your target, then you can choose multiple targets to uber to reload their ammo. This is called uber juggling
How to do itIt is pretty simple. If you see your friend/teammate on the verge of running out of ammo, you simply take your medibeam off your main target person and click on him once. By doing this, your friend's ammunition would be full again, and chances are, your main target won't die. This is extremely useful, and may be a little tough for beginners to do. However, practice makes perfect, so just go onto some servers and play as the medic. Most CP maps are pretty good to practice medic, because they involve having to heal hordes of teammates at a time.
Signs to not uberSometimes, ubers can be wasted by the efforts of the opposing team, or maybe just the terrain. Here are some tips and tricks on when not to uber.
1. Do not uber if there is an experienced pyro standing behind a crate that is in front of you. When you uber, all he has to do is hit m2 and he can push you out of the way, thus wasting your uber. This is a sly trick, and I use it a lot. A pyro's airblast can really mess with the communications between you and your uber patient. You would probably want to clear the crate before ubering, so you can't mess with the uber too much.
2. Do not uber an inexperienced player. You have to judge a player's skill and make the decision on whether to uber or not, depending on situation. If you are low on health, pop it. If you are fine, and there is someone else to uber, uber them instead. I have ubered some players, who then react like its a poisonous gas or something coming onto them, and they run for their lives. Make sure that they understand what an uber is before ubering them.