Not to be confused with the famous game of the London Underground, this has come to me by word of mouth from (apparently) a BBC radio program of some sort.  The premise is very, very simple:

Going around in a circle, each person says a word or short phrase.  Each new phrase must have nothing whatsoever to do with the previous phrase.  Anyone who says something that could be connected to what was said before them is excluded from play.  In the end there can be only one.

Fictional example wrote: A: Justice...
B: Yuri Gagarin...
C: Cheerios.
D: Martial Arts.
A: Thistles.
B: Dromedaries!
C: Sand ... damn!  I'm out.
D: Fisherman knit sweater...
A: 5 a.m....
B: Mornington Crescent.
D: You're out.
B: I'm what?
D: 5 a.m. in the Mornington?  Do I really need to spell it out?
B: Ouch!  That's awful.
D: Bamboo...
A: Siberia...
D: Jellyfish.
A: Wireless Networking.
D: Legos
A: Forest spirits!
D: Marmalade!
A: Compact discs!
D: Bifoca... ah DAMN!  They're both glass products.
A: Nicely played.

This warmup is hard.  Harder than it looks.  Give it a try, it's like Jungle Speed for your language centers.

I think that it encourages engagement with what other people are saying.  I also think that it works your pattern-finding centers in two distinct and antithetical ways (that's why it makes your head hurt so much):  first, you're looking for patterns between what people are saying, so that you can get them out.  But second, when you get your turn, you're very, very quickly searching whatever phrase you had in mind for possible connections, and if you find them you're discarding that phrase and trying to think of a new one fast.