The list here is not meant to be a complete list, just a taster of objects in the Solar system, if you think of something that needs to be added then add a comment and I'll update the list.
The largest planet in the solar system is Jupiter which is the fifth planet from the Sun. It is considered to be a failed star, not having the sufficient mass that was required to start nuclear fusion. The smallest star so far discovered, ELBM J0555-57AB which is not in the Solar System is smaller than Jupiter but has more mass. Jupiter is also the largest planet with a ring system, the rings were discovered by Voyager 1 as it flew past. The largest rocky planet is Earth, just slightly bigger than Venus.
The smallest planet in the Solar System is Mercury after Pluto was downgraded to dwarf planet status in a controversial vote by the International Astronomical Union in 2005. Mercury is also the smallest rocky planet in the solar system. The smallest gas giant is Neptune at the very edge of the solar system.
Although I have covered this previously in the article, What are the Largest Moons in the Solar System, I'll just do a very brief coverage. The largest moon is Ganymede which is a moon of Jupiter. Our our moon, the moon is the largest in comparison to the planet it orbits.
As for the smallest, some of the moons around the planets are mere specs, based on the data I have, the smallest is S/2009 S1 which is smaller than a kilometer. I don't have all the moon radiuses in the database so that's my best answer. It is a moon than orbits Saturn.
There is only one star in the solar system and that's the Sun so its both the largest and the smallest star in the Solar System. nemesis is a hypothetical brown dwarf that's not been proven or disproved as yet. The question is whether it is part of our solar system is not, it is believed to come close every so often and is accused of sending the comet that killed the dinosaurs.
The largest asteroid that we've discovered and has been upgraded from asteroid to dwarf planet is Ceres. When it was first discovered, Ceres was classed as a planet then in was downgraded before being upgraded. Ceres is the only asteroid that is spherical in nature in the asteroid belt between Mars and Jupiter.