Dust off your old Deus Ex CD, install it with WINE (which works fabulously), update to the mp patch if needed, install Microsoft Redistributable C++ 2005 and install The Nameless Mod.
It's a pretty big download (the .iso weighs in at over 1.3GB, the executable is over 900MB -- install space of about 3.5GB) so I hope you're not still using that old 9600 baud modem ...
Hope you get as much fun out of playing it as it was to develop.
http://thenamelessmod.com/
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