If Charles is King and by chance Andrew is dead, the traditional title of the second son, Duke of York could be bestowed on Harry. But, with two "of York" princesses still lolling about, it might be a complete impossibility.
Sussex seems most likely. The last dukes of Clarence and of Albany both have unfortunate reputations attached to them and seem unlikely choices.
Odd tidbit: traditionally speaking, the second son of the Monarch has the Duke of Clarence title bestowed upon him. The Duke of York title being bestowed to the second son came about with HM's grandfather because he himself was Duke of York by his grandfather and his older brother was given Duke of Clarence (since he was second in line at the time) with their father being Prince of Wales. They were quite young when given the titles, so once their father came to the the throne, he was known as Edward VII. Duke of Clarence gave up on the title and moved one up and became Prince of Wales, but George couldn't just drop his dukedom since he was the brother of the future king and his father did not wish to give him a new title since he was quite young and rather reserved the title Duke of Clarence for the Prince of Wales' son.
It is a Hanoverian tradition that the second son is Duke of York with only the the past three generations being named that way. The reason they changed it is because Victoria broke with tradition and named her second son Duke of Edinburgh and Earl of Kent. So HM naming her consort the Duke of Edinburgh is actually a VERY high honor and usually resorted for those in the line of succession instead of consorts. She also broke again with tradition naming Edward Earl of Essex.
But generally speaking,
1) First in line --Prince of Wales & Duke of Cornwall
2) Second in line- Duke of Clarence
3) Third in Line - Duke of Bedford
4) Fourth in line- Duke of Gloucester
5) Fifth in line- Duke of Kent
The Cambridge Title was actually reduced to a Marquessate. It became abolished with the extinction of Germanic titles. HM basically eliminated the Marquess of Cambridge as it derived from Duck of Teck (again Germanic title instead of British) and gave William a ducal title.
Forgive me, if I'm mixing things up here, but I always thought that the problem with Albany and Cumberland was that technically there're still heirs for the titles (Coburgs and Hannoverians) and that despite of being stripped of those titles during WW1 they could actually demand it back or even try to use it without approval. I don't think they will do either of it, but obviously the Queen wouldn't want to try.