Most Tabletop Games have sets of pre-molded models available to play with. These may be sold by the company that makes the game, or by a secondary company that's licensed to provide official products, or may be models either designed without a specific game in mind or lifted from their intended game to another. These vary in overall quality, but often look very nice. For some games, particularly Warhammer and Warhammer 40000, conversions are not only encouraged but oftimes pretty much necessary for gameplay reasons. Orks are probably the best example of this and all the more awesome for it.