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Plant cells often have a large, specialized vesicle called a central vacuole.

The central vacuole is a fluid-filled organelle that may be found in mature, living plant cells. Central vacuoles are created from the merging of smaller vacuoles, and perform many functions:

The central vacuole stores important organic compounds like proteins (especially in seeds), amino acids, and sugars.
It is also the plant cell’s main storage site for ions, like potassium ion and chloride ion.
The central vacuole can also be used as a disposal site for toxic wastes/metabolic by-products of a plant cell.
Central vacuoles can contain pigments that give petals their color.
Furthermore, because the plant cell has no lysosomes, the central vacuole does some of the digesting of organic compounds as well.
The central vacuole is mostly filled with water, so as it enlarges it increases the turgor pressure inside the cell, which helps maintain the sturdiness of the plant. Because it takes up most of the space in the center of the cell, the central vacuole also increases the surface-area-to-volume-ratio of the rest of the cytoplasm, which improves the efficiency of nutrient uptake.

Many freshwater Protists, like paramecium, have contractile vacuoles for pumping water out of the cell. The need for contractile vesicles is because freshwater Protists live in a hypotonic environment and thus water always tends to move into their cells. The contractile vacuole is thus essential for osmoregulation: maintaining the appropriate concentration of salts and other molecules in the cell, which is essential to the cell’s survival.