'Barrett' at Blue Technoids has successfully compiled (GCC2) Open Arena for Haiku, but it remains untested because he only has VESA mode available. The data package for the game weighs in at >300mb and looks very pretty (hehe):

{rokbox title=|Open Arena Screenshot :: Sexy| size=|800 600|}images/stories/news/06-09/angelyss-dark.jpg{/rokbox}

You can find requirements and installation instructions on Blue Technoids Wiki.