One of the Fox 32's if you're looking for something on the XC/trail side...Rock Shox Lyric if you want more of a trail/AM fork...or a Fox 36 if you want an AM/FR fork.
well if you want to do XC don't buy a battery....its heavy and requires MRP cromoly cranks with super wide axle to clear the swingarm - which makes the bike even heavier and gives a really wide Q factor for pedalling...
Battery is designed very specifically for slopestyle / dirt jump riding!
there are much better choices for all round bikes that will let you do XC and light freeride, look at the Specialized Pitch for example