Android #18 is one of the stronger androids that Dr. Gero created for the pourpose of killing Goku. Not only is she strong but she is also the prettiest of all of the androids (duh). Krillen fell for her at first site and ends up marrying her and having a kid at the end of the series. She is almost killed by Cell when she is absorbed, but right before Cell dies he spits her back out.