The modding support for Fallout 3 is simply amazing. My favorite mix is Book of Earache with Fallout Wanderer's Edition, in the end you get like 300 real-life guns with multiple features like grenade launchers, switchable fire modes etc, and survival (FWE) which allows for a more realistic gameplay.
Sucks that there's no big pack for armors though - most of armor mods = fap material only compatible with female characters. FOOK2 adds shitload of armors for both females and males, but it conflicts with BoE.