OD&D: Hex crawl rules and overland adventures.
B/X: XP for Gold and less XP for monsters.
1E: Separate Race/Class
2E: ??? - not sure - don't have a lot of experience with this edition.
3E: Ascending AC and Base Attack Bonus
4E: ??? - not sure - to be honest, there is very little from this edition that is appealing to me.
5E: Bounded Accuracy
B/X: XP for Gold and less XP for monsters.
1E: Separate Race/Class
2E: ??? - not sure - don't have a lot of experience with this edition.
3E: Ascending AC and Base Attack Bonus
4E: ??? - not sure - to be honest, there is very little from this edition that is appealing to me.
5E: Bounded Accuracy