The singularity.* The mysterious center of the black hole, whose atomic bonds have broken under the massive force of gravity to create a point of infinite density, from which nothing can go fast enough to escape - not even light. Yet, they are the only objects in the universe that are powerful enough to spawn galaxies.
For Deleuze the singularity is a metaphor. It represents those (singular) objects, people, events - small fragments of space/time - where multiple threads converge, and from which many new threads may arise.
The singularity itself is an assemblage, but an assemblage so densely packed that it is easily mistaken for a unity. Think of the film Avatar. Hundreds, maybe thousands of different ideas, technologies, emotions, and histories came together into a single object/moment: Western noble savage romanticism and nature worship; special effects technologies; the Military-Industrial complex and the Peace movement; indigenous movements; Capitalism and the petroleum fueled industrial economy; the Hollywood movie mega-machine; ecology, Gaiaism, and environmentalism; James Cameron; white messianism; hyper-reality; Liberal/Conservative politics; the mining industry; Anthropology and many others.
But the singularity is also a point where innovation and uncertainty enter the Universe - in the words of Complexity and Chaos, a bifurcation. Avatar again - it spawned myriad new threads: academic/philosophical discussions; publicity and a potential communicative link for indigenous movements; novel special effects technologies; debates about environmentalism; discussions of colonialism; new psychological disorders; marketing tie ins; etc. The film is not any one of these things, but a multiplicity converging and diverging upon a single point - the singularity.
The value of the singularity is that it can be a point of intervention. Change happens so rapidly, so intensely like the explosion of a supernova fusing atoms into heavier elements and raining them down upon the surrounding universe. Recognizing a singularity, one could catch hold of a thread and try to maneuver it towards some goal. It's not a guarantee of success - there will always be others pulling in different directions and there's always an element of uncertainty - but the singularity is ripe with potential.
*not to be mistaken with Ray Kurzweil's Singularity