Bladestorm [http://en.wikipedia.org/wiki/Bladestorm] is really good fun.
It's set during the 100 Years' War between England & France, and the core game-play takes place on battlefields, where you control a mercenary and take command of different squads of infantry & cavalry, but you can join and leave any squad at any time.
It's 3rd person, and a mixture between strategy and hack'n'slash.
Each different squad you control has advantages & disadvantages against other types of units, e.g Pikes are effective against Cavalry, Swords are a good all rounder, Swords & Shields are basically like riot police, Halberds have high attack but are slow with low defence, Longbows have superior range and act like artillery, but are weak in melee, Short bows have short range but a fast rate of fire, Crossbows are good against armoured units... it works on a paper, scissors, stone principle, but with tactics like flanking, higher ground, charging, and experience/levelling comes into play too (like a level 99 Calvary unit can charge headlong at a level 20 Pike unit with impunity).
There's a great variety of different weapons and exotic mercenary units from around the world, like Camel cavalry, Elephants, Samurai, Vikings, Berserkers, Ninja, Abyssinians, Indians, Romans, Mongol mounted archers, Arabians...so it's not just your typical European medieval units.
I thoroughly enjoy it, I've put over 120 hours into it and I've still not finished it, I'm taking my time levelling up and acquiring all the weapons etc, but there's also a big end game once you've finished the main story arc.
If you've got a 360 or PS3 then I wholeheartedly recommend it, but you should check out the demo if you can.
