organisms that some people form a Special Interest^TM over

slime molds

Viruses are more abundant than any other biological entity, with 10³¹ existing on Earth.
Just like there's a human microbiome, there's also a human virome. [2] There are approximately 40 trillion bacteria in the human body, and viruses number 10 times that.
Although viruses are extremely small, some organisms eat viruses, mostly for their nutritional value.
Viruses are diverse, with there likely being millions of types of viruses. [2] However, only ~16,000 have been described in detail or sequenced.
Human understanding of viruses is gaining a LOT of speed in ~2025 due to the availability of newer DNA techniques: (see also: ▶viral dark matter [▶2])