Difficult question because they are all pretty much the same! If I had to pick one, and I can’t pick the Sun (the Sun is obviously the most important star for us because it is ours! But, picking the Sun would be a bit boring, right?), then I would pick Betelgeuse. Betelgeuse is cool for a range of things, firstly it is cooler than a normal star. Cooler in that it is colder than a normal star, that’s why it looks red when most of the other stars in the sky look blue or white (red stars are colder than white which are colder than blue). Second, it is huge! It is about 8 times the mass of the Sun but more than 1000 times as big! Why is it so big? Because it is almost out of fuel and when stars run out of fuel they expand a lot. If Betelgeuse were where the Sun is, the Earth (and most of the other planets) would be inside it! Finally, because it is running out of fuel and so massive, it is one of the best candidates we know of to be the next supernova in our galaxy, i.e. the next nearby star to explode, which will be very cool to see because when it explodes the explosion will be so bright that we could actually see it during the day!