Class G stars are yellow and yellow-white stars. Our sun is a Class G star. Most Gs are main sequence dwarf stars, more properly classified as G V Stars. About 1 in 13 main sequence stars in our part of the galaxy are class G.
Very few giant or supergiant stars are class G. There exists a condition known as the "Yellow Evolutionary Void". Basically, supergiants swing from Class O or B into Class K or Class M and back, without stopping in Class G. If they exist as a Class G, it's only for a very short amount of time (especially when considered in the life span of a star). G class just isn't a stable condition for really big stars, and may lead to a Yellow Supergiant going Supernova.
Specific named Class G stars
- Alpha Centauri A
- Capella (specifically α Aurigae Aa is a yellow giant, and one of the stars making up that system)
- Tau Ceti