Very few, at least for STEM fields. If you look at notable scientists in any given field, their main contributions were in their expertise area before the thing that made them famous. Teller had already made serious contributions to physics before the atom bomb. Jennifer Doudna (CRISPR, CAS9) was the first to see the structure of RNA (except for tRNA) using an innovative crystalline technique. Planck is mainly known for quantum physics, but made huge contributions to the field in general.
It's hard to think of many famous scientists that weren't already well known in their field. Some stand out. Einstein, for example, had a fairly lackluster career until his Annus Mirabilis papers. Mark Z. Danielewski (House of Leaves) bounced to and from various jobs. But largely, the idea of the brilliant outsider is like the 10x engineer. It exists, but is rare.
Even Einstein I would not say didn't have formal training. He had been in and around academia for most of his life. He was obviously far ahead of the curve, but he did accumulate the formal training. His stint in a regular job was more of an anomaly than his affinity to academia and physics.
Right, even Einstein had some serious academic training and mathematical chops. But I would argue that he was a bit of a wild card, because he was unable to secure a teaching positions and looked very mediocre from an academic perspective. But fair point, even the geniuses had formal training and instruction.
It's hard to think of many famous scientists that weren't already well known in their field. Some stand out. Einstein, for example, had a fairly lackluster career until his Annus Mirabilis papers. Mark Z. Danielewski (House of Leaves) bounced to and from various jobs. But largely, the idea of the brilliant outsider is like the 10x engineer. It exists, but is rare.