The Bubble Tip Anemone (Entacmaea quadricolor) has the reputation of being one of the easier sea anemones to keep and comes in a few different colors or varieties.
There are many clownfish species that will host with this anemone (see below), with the most common being the Maroon Clownfish.
You don't need to have a clownfish to keep an anemone, though watching the symbiotic relationship between the clownfish and the anemone is one of the most fascinating aspects of aquarium keeping. The opposite holds true as well. You don't have to keep an anemone if you want to keep clownfish.