My “favorite” is impossible to pick, but I am happy to respond with one cool microbe:

Pseudomonas syringae: This species produces ice nucleation proteins that allow water to freeze a few degrees above 0 °C. These bacteria will grow on the surface of a plant, and when the temperature approaches the freezing temperature ice crystals will form around the bacteria and the sharp crystals will damage the plant tissue - giving the bacteria an opening to infect the inside of the plant.

This ice-damage trick is cool… But what’s even crazier is that these bacteria can be picked up by air and taken high into the atmosphere, where they can resist the excessive radiation and eventually catalyze the formation of ice crystals around them in the clouds. These bacteria are thought to contribute - and not insignificantly - to the formation of rain. They are also found in the core of a large percentage of snowflakes and hailstones. And these bacteria are even used for making snowpacks.

I think that such a ubiquitous microbe with ice super-powers is pretty cool ^_

You can read the wiki page for much more information and citations: https://en.wikipedia.org/wiki/Pseudomonas_syringae