Probably the most common example is condominium homeowner association (HOA) elections. For a building with multiple condominium units, the building will often need to make decisions, such as to charge each owner an additional fee to replace the roof. To make these decisions, the HOA will have trustees who are elected by the condo owners to make decisions. The trustees will generally be a subset of the condo owners.
Because the condos in the building have different sizes, each condo owner is assigned a weight corresponding to the size of their condo. For example, the weight of a vote may be the same as the square footage of the condo, and a person with a 2000 sq. ft. condo will have double the voting power of a person with a 1000 sq. ft. condo.