1) The reproductive cells in multicellular organisms.

2) Gametes, also known as sex cells or germ cells, are the cells that come together during fertilisation or conception in organisms that reproduce sexually. Their genetic complement consists of a single set of unpaired chromosomes. (from Wikipedia)

3) Mature male or female reproductive cell (sperm or ovum) with a haploid set of chromosomes (23 for humans).

4) A reproductive cell of the body. Germ cells are egg cells in females and sperm cells in males.