Gilmour used a Binson Echorec. Unless you want to spend (manymany) thousands for -THE- sound, the easiest way to do the Gilmour sound is run 2 delay/echo units. A dark analog one and a brighter digital one. I personally turn to the Carbon Copy because it's warm and very versatile with the mod button, but just as many people go Memory Man. Both are awesome. As for digital, Boss units like the DD-5 or DD-20 are great. Between those, you should nail all the sounds in the basket you want, without grabbing towards U2 sounds (who used a TC 2290, in which case you might wanna look at something like a Nova Delay instead of a DD-20).