No armour, both at full health.
1. No prep just a straight fight with a sword for Aragorn and an arakh for The Khal, starting 10 feet from each other.
2. 24 hours prep, but no help for either side.
3. Drogos army vs Gondor in open battle.
Personally I think Drogo takes 1 and edges 3, and Aragorn edges 2, but I think all 3 are fairly even and I'm open to persuasion.
Oh and it's TV vs Film, and Book vs Book, so please explain which you believe would win each and why.