Mechanics Needing More Than 2 Players (fan-made expansions)

[loganmann1]

There are many mechanics presented across the various expansions that have been made by fans of Carcassonne.  They range in styles of play and everyone has their preferences.  For this question I’d ask if preferences could be set aside.  Also, I’m asking this by mechanic instead of by expansion because so many expansions can be broken apart into separate parts.

My question is…1) Which mechanics among the fan-made expansions here on CC really work best (even require) more than 2 players to be effective?

(I've started a separate thread for discussion concerning the official expansions)

I ask this question  1) coming from a background of generally 2 player games 2) not having the resources to make everything.  The question is often asked what works well with 2 but I wanted to turn it around to help identy what might require more then 2. My thought and hope is that this discussion might be a helpful resource for helping people choose expansions and mechanics that will work well for their groups so they can get the best experience out of making fan made expansions.

So what are your thoughts?