Missing the Talon of Horus?? I would say it is a must read for any BL fan now.
The rest of the Gaunts Ghosts novels, you seem to be missing The Saint omnibus, which is odd, as you have The Lost. Have you lost it, or at least read the four novels contained with The Saint arc? Otherwise that would be very confusing. Also Salvations Reach, which comes after Blood Pact.
I quite liked the Sundering triology from the Time Of Legends series. Malekith, Shadow King and Caledor.
Battle of the Fang has been mentioned, as has Ahriman.
Titanicus, is also quite a good read, you seem to like Abnett, so would enjoy it no doubt.