Some books I always wanted that have already been mentioned...
Killer Croc / Jason Todd introduction
agree with toni this is an excellent little arc, very representative of a cool period in Batman comics and Crocs never been in a better story. Also a great villain, the Squid
Classic story! Culmination of the Pre-Crisis Batman mythos, the original prison break, a hundred Batman villains, also probably the best cover in Batman comics ever
Neal Adams Illustrated in original condition
The new prints are just abominable. I wonder how much clout Adams has left with DC after Odyssey. I don't see why it should be so hard to convince Adams or anyone at DC to do this, just repackage and market as a celebration of the original era and production style - are they allergic to money?
Nocturna / Nightslayer / Jason Todd saga
This would probably need like three volumes, and never sell, but hey
Peter Milligan run
Already made a thread about this!
Moench Jones run
Cherry pick the best issues, featuring Killer Croc, Penguin, Deadman, Scarecrow, Freeze, Ragman. An excellent look back here
Featuring the Crusader and Guillem March, collect it with the Frazer Irving illustrated origin mini and put "As seen in Arkham City" on the cover.