I've shared my favorite mod on Reddit/r/fallout. My all-time favorite mod ever is a Fallout 3 mod that combined the game with the Cube movie series. The mod adds an underground facility like the one in Portal 2 that can be explored and has been filled with some puzzles.
My reddit post:
Reddit.com
The mod:
Nexusmods.com?
crayak1431967226
Carlo joined
<a class="bb_link" target="_blank" href="https://www.youtube.com/watch?v=aTBGcSyy-jU" > Play this while reading (youtube)</a> <br> <br><img src="http://steamcommunity-a.akamaihd.net/economy/emoticon/MrFoster" class="emoticon"> <i>Ladies and Gentlemen, Children of all ages! <br>May I welcome you this evening to another great event of pleasure and joy? <br>An evening, you will nót soon forget! </i> <br> <br> <b> <i> Witness The Unusual! </i> </b> <br> <i>¤ The Girl with two heads</i> <br> <i>¤ The Amazing Mechanical Man</i> <br> <i>¤ The Incredible Man Monkey</i> <br> <br> <b> <i> Witness The Disgusting! </i> </b> <br> <i>¤ Pukey The Clown</i> <br> <i>¤ The Bearded Beaty</i> <br> <i>¤ The FrankenPounder</i> <br> <br> <b> <i> And kill it! </i> </b> <br> <br> <i>Ladies and Gentlemen; step right up to the three ring circus of death!</i> <br> <b> <i> Welcome to, <a class="bb_link" target="_blank" href="https://www.youtube.com/watch?v=X9DXb_GUotg" > the Abusement Park! </a> <img src="http://steamcommunity-a.akamaihd.net/economy/emoticon/ccskull" class="emoticon"> </i> </b> <br> <br>("<img src="http://steamcommunity-a.akamaihd.net/economy/emoticon/blue" class="emoticon">..<img src="http://steamcommunity-a.akamaihd.net/economy/emoticon/blue" class="emoticon">)