Freespace 2
http://www.gog.com/en/gamecard/freespace_2
Buy it from there, download the FS2_Open engine and all the enhancements from http://www.hard-light.net/, grab the Freespace 1 Conversion mod from there as well, and enjoy.
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"I'm Commander Shepard, and you're standing in the biggest library in Citadel Space. Look me up."