I always love the band's unspoken interactions with each other. Take for example when Bono wants to expand on a lyrical idea or extra tracks during a live performance. All he has to do is hold his arm out to signal to The Edge and others that he's going to extend the bridge (or whatever part he's on). That's all it takes and the rest of the band takes the cue. For any one who's played live with a multiple people, you know that's really hard to do and find your bearings. With the chemistry of U2, it's effortless.
There are lots of examples, the best one being during the Fuck the revolution part of Sunday Bloody Sunday in Rattle & Hum. Bono had more to say and communicated that by raising his arm - Larry picked up on it and continued his martial beats. Once he did that, The Edge noticed it and looked at Bono and he plays another bar of the bridge. A sign of a band who's members are totally interlaced.