In humans, the haploid phase of the lifecycle is single-celled, while the diploid phase is multicellular. In contrast, in mosses and fungi the haploid phase is multicellular while the diploid phase (sporophytes/zygote) is single-celled.
Red blood cells are discussed in the article.
The unfertilized eggs of bees become drones, so they must be alive. As a side effect, this indirectly make bee-like insects evolve a lifestyle with a big colony with a queen.
In fungus, most of the life is as haploid (i.e. a single copy of the chromosomes, like sperm and eggs) instead of diploids (i.e. two copies of each chromosomes, like most of our cells.)
In some ¿unicellular organism? [I can't find a good link now] the haploid and diploid versions are almost equal.
[And plants are also weird, some have 4 or 6 copies of the chromosomes instead of 2.]