On the Pulse album, you can hear almost the entire audience singing along to "Wish You Were Here", in tribute to Syd Barrett.
Roger Waters' speech at the end of "Outside The Wall" at London's O2 Arena, in his Wall tour, where David Gilmour played and sang on "Comfortably Numb", then joined Waters and Mason at the end of the concert:
Roger Waters: "Thirty years ago, when Dave and Nick and I first did this...uh, with Rick...I was a rather grumpy person and disaffected with rock and roll audiences...and put young David to the test...BUT ALL THAT'S CHANGED! I could not be happier to be with you, and these three guys (points to Gilmour and Mason), and all thirteen of us here, (points to his backing musicians), and you tonight, thank you very much indeed!"
The knowledge that David Gilmour personally made sure Syd Barrett would receive his share of royalties after he left the band.
After the publicity of the Live 8 reunion boosted sales of Pink Floyd's EchoesGreatest Hits Album, David Gilmour encouraged himself and the other members of the band to donate their earnings to the Make Poverty History cause, and for other acts on the bill to do the same, feeling that it was money which "should be used to save lives".
The reunion itself for that matter; the various members of the band had not been on great terms for decades, with Waters even taking Mason & Gilmour to court over use of the band's name in the 80's, and it was said that pigs would fly before they'd play together again. They put some pretty large differences aside to do so.
In 2003, Gilmour also donated a $3.6 million dollar mansion in Maida Vale that he bought, but never used, to the ninth Earl Spencer to be used as a homeless shelter.