Dungeon Crawl Stone Soup is an open-source, single-player, role-playing roguelike game of exploration and treasure-hunting in dungeons filled with dangerous and unfriendly monsters in a quest to rescue the mystifyingly fabulous Orb of Zot.

Upstream: http://crawl.develz.org/wordpress/

This version is very recent (August 2011) and has only console version, no menu entry.
Tune font, toggle fullscreen on and start game:
Game will crash if you change font/fullscreen during game play.

[EDIT]
First start will take several minutes (thanks szopin for pointing this).

Enter is fixed for N900, so 'enter' will not work over ssh (game running on N900, player using computer's keyboard).
[/EDIT]

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For developers:
There are also package crawl-tiles, started with /opt/crawl/bin/crawl-tiles , which is using GLES, but it crash immediately when starting. If you know something about GL/GLES wrapping, step in.