What teachings do all schools of Buddhism share?

The common teachings of all Buddhists are:

• The ordinary lot of human beings is to be suffering from a delusion about the real nature of the universe;

• A method for dispelling this delusion was originated by someone called "The Buddha" who employed it to purpose;

• Buddhism offers to teach the adherent this method so as to cease being subject to the delusion.

Other than these rudiments, all other teachings are variably composed, and supposed literal or metaphorical in their application of instruction. They amount to catechisms of formal doctrine without common confidence or consistency as to their meaning.

There might be many school with many different ideas, some following the Buddha and serving the Dhamma and Vinaya, some using it as base for own ideas. Once the Buddha was asked by his former foster mother, Ven Gotami, in regard of how to recognize whether teachings are Dhamma-Vinaya (the name the Buddha gave his founded religion) or not. He answered:

"Gotamī, the qualities of which you may know, 'These qualities lead to dispassion, not to passion; to being unfettered and not to being fettered; to shedding and not to accumulating; to modesty and not to self-aggrandizement; to contentment and not to discontent; to seclusion and not to entanglement; to aroused energy and not to laziness; to being unburdensome and not to being burdensome': You may definitely hold, 'This is the Dhamma, this is the Vinaya, this is the Teacher's instruction.'"

Possible supportive Introdution to Dhamma-Vinaya.

Maybe worthy to think about is, that certain definitions like such as Buddhism and what might count as such... the standards as well as the orientation, are for the most later development, now also strong dominated by lay people and many various ideas and objectives behind.

The lesser the bound and regard torward the ancestor, elders and leaders, to more it goes astray and it, by time, becomes more and more difficult to find common ground, common objectives and common ways. Lucky if finding a paricular Sangha (monastic disciples) of common offiliation which carries on the heritage. It's worthy to note that the Buddha gave the surviving of the truth and way to it, Dhamma-Vinaya, at least more importance than unity, although he gave very concerning the best tools to handle unity and give into it.

[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]

In all seriousness, i think the common teaching in both the meaning & expression is; "there once lived a man from Sakyan clan who achieved something special and it was very good"

There is no consensus on what he actually achieved.

I guess there is also consensus on him having some magical powers in general and it all having to do with some kind of meditation.

I'd say nothing, there are so many sects, that you can find any Buddhism that lacks one element or the other.

• Meditation (less common, matra and mudra)
• The Historical Buddha. In some forms of Buddhism, the historical Buddha is not so important.
• Monasticism and renunciation.
• Philosophical bent that cares about topics like identity, change and it's application towards dealing with suffering.

But right off the top of my head, Shin de-emphasizes meditation, SGI deemphasizes monasticism, the Buddha of, say the Lotus Sutra, isn't really the same guy as the Buddha of the early Pali texts, and traditional lay Buddhism doesn't involve much philosophy.

The phrase that comes to mind when I'm reading about yet another sect or school of Buddhism, is "recognizable Buddhism."

As well as the list which is quoted in Unrul3r's answer there are, also, three other lists included on Wikipedia's Basic points unifying Theravāda and Mahāyāna article.

A less canonical list was written by Christmas Humphreys,

In 1945 he drafted the Twelve Principles of Buddhism for which he obtained the approval of all the Buddhist sects in Japan (including the Shin Sect which was not associated with Olcott's common platform) of the Supreme Patriarch of Thailand and leading Buddhists of Sri Lanka, Myanmar, China and Tibet.

Here for example is a link to the Twelve Principles of Buddhism By Christmas Humphreys.

They include (I summarize, see a reference for the more-complete text):

1. Self salvation is for any man the immediate task. (Parable of the Arrow)
2. The first fact of existence is the law of change or impermanence. (Therefore clinging to form causes suffering)
3. The law of change applies equally to the "soul". (Therefore non-self)
4. The universe is the expression of law. (Kamma, purifying inner nature, liberation from rebirth, ultimately every form of life will reach enlightenment)
5. Life is one and indivisible, though its ever-changing forms are innumerable and perishable. (Compassion and harmony)
6. Life being One, the interests of the part should be those of the whole. (Selfishness is caused by ignorance; the four noble truths)
7. The Eightfold Path consists of: etc. (The way is to be practised, not just theory: "Cease to do evil, learn to do good, cleanse your own heart: this is the Teaching of the Buddhas")
8. Reality is indescribable, and a God with attributes is not the final Reality. But the Buddha, a human being, etc. (The Buddha became enlightened and tought that nirvana can be achieved on earth)
9. From potential to actual Enlightenment there lies the Middle Way, etc.
10. Buddhism lays great stress on the need of inward concentration etc.
11. The Buddha said: "Work out your own salvation with diligence". Buddhism knows no authority for truth save the intuition of the individual, and that is authority for himself alone.
12. Buddhism is neither pessimistic or "escapist", nor does it deny the existence of God or soul, though it places its own meaning on these terms.

I can't say that "all schools share these teachings" but apparently, at least, these teachings are compatible with all the schools'.