I assume you mean beneficial to humans?
Viruses make up a large portion of Earth's ecosystem, and a large class of them help keep bacteria in check.
https://en.wikipedia.org/wiki/Bacteriophage
There are even efforts to try and harness them to treat bacterial infections.
Additionally, a good chunk of our DNA is from ancient viruses, so homosapiens wouldn't be what we are today without viruses.
That's the case for most species.
As a very specific and highly functional example of critical viral proteins in other organisms, there wouldn't be any placental mammals without viruses. https://en.m.wikipedia.org/wiki/Placenta
Mammalian placentas probably first evolved about 150 million to 200 million years ago. The protein syncytin, found in the outer barrier of the placenta (the syncytiotrophoblast) between mother and fetus, has a certain RNA signature in its genome that has led to the hypothesis that it originated from an ancient retrovirus: essentially a virus that helped pave the transition from egg-laying to live-birth.
Viruses affect other things too, including bacteria! Bacteriophages are the first to come to mind
https://m.youtube.com/watch?v=SbvAaDN1bpE
Sorry to link to a video, but this recent Kurzgesagt video covered your question pretty closely :)
There are viruses that make some plants look more appealing to some people. For example they are the cause of these striped patterns on tulip petals.
https://www.youtube.com/watch?v=YI3tsmFsrOg
There are beneficial bacteriophages for humans and other animals and plants.
Probably, yeah. Their whole schtick is to move DNA around and fuck up genomes n shit. They’re evolutionary drivers.
There is the "Luck Virus" and "Sexual Magnetism Virus" poor Rimmer
This has made Mr Flibbles very cross!
I had hoped a few would get this
Some viruses are useful for studying genes - you can make them transfer a genetic sequence into a cell.
They can be used in gene therapy - a very promising field of medicine.
And some viruses could also be used instead of antibiotics, which could potentialy solve the resistence problems and also help avoiding collateral damage to symbiotic bacteria. (Research of this technology is quite old, unfortunately it was abandoned for a long time and everyone focused on antibiotics instead.)
