I already mentioned his use and arrangement of that Harry James in Body Heat and the Romance for Guitar and Orchestra from Deadfall.
Both of these examples showcase Barry's ability to use and, in the case of Deadfall, compose source music that works dramatically.
Another example, from very early in his career, is The L-Shaped Room, his first film for Bryan Forbes. Barry was brought in to provide two jazz pieces in a club with Brock Peters playing the trumpet. Catchy and atmospheric, these two wonderful pieces--oddly enough--have never been commercially released. Very strange when considering that they were dome in a period when JB was much better known as a recording artist than a film musician and releasing singles was pretty much the norm. What a nice single these two tracks would have made. Also, never on CD.
Hard too say - it would probably be Dawn of the Dead because it has numerous source music that wasn't done by Goblin like the shopping mall stuff, I would dig a full release of that score but I know it'll never happen in this life-time or next! Pity!
I assume you’ve heard of the Second Sight 4K release in the UK?