I have to say The Heart of Midlothian comes to mind. I've long wanted a Halo themed horror game, and the story of the Midlothian's downfall is just ripe for exploration and inspiration. Both the written story and animated short were fantastic.
The Say My Name comes to mind as well, as it's an awesome ship that leads into my favorite Halo campaign.
The UNSC: Heart of Midlothian was a wonderful tale. I did not read the short story, however, I did see the animation and I loved it. The ODST Baird was a badass who gave his life to save the navdata and it just shows how some soldiers go unnoticed in canon who sacrifice it all and it’s sad to see.
As for the UNSC Say My Name, correct me if I’m wrong, but did that ship either, a) participate in the Battle of the Rubble along with the Spartan-II Grey Team and the Rubble Security Council against the Kig-Yar and Grunts in The Cole Protocol Novel, or b) hold the contingent of ODSTs from the 65th Shock Troop Division to assault the Covenant Carrier the Solemn Penance via orbital insertion to capture the Prophet of Regret? If it is option b) that would be pretty significant as it held Alpha-Nine the team that was responsible for bringing Quick to Adjust (Vergil) to safety from the cities inevitable glassing by the Covenant in search for the Portal at Voi. Nonetheless both ships are a vital part of Halo lore and both have served well during the years they’ve been active.
EDIT: I just reread what you said and there was no game that occured after The Battle of the Rubble. I also went on Wiki and did some research and it turns out I got confused in my lore with The Midsummer Night and Say My Name... whoops. It was the Midsummer Night’s crew present at the Battle of the Rubble leading into the Battle at Messite which saw the destruction of the Unggoy army Reth was making.