There isn't one single cell type that is universally the fastest. It depends on what you consider "moving quickly" and the specific environment. However, some contenders for fast-moving cells include:

* Sperm cells: These cells are designed for speed and have a whip-like tail (flagellum) that propels them through fluids.

* White blood cells: Some types of white blood cells, like neutrophils, can move quickly through tissues to reach sites of infection. They use a process called amoeboid movement.

* Eukaryotic cilia: These hair-like projections found on the surface of some cells can beat rapidly to propel the cell or move fluids around it.

* Prokaryotic flagella: These whip-like structures are found in some bacteria and can spin rapidly to propel the cell.

Ultimately, the fastest-moving cell will depend on the specific context and the criteria used to define "speed."