Dead Rising 3

If you want to power through this quickly, work toward building some of the stronger combo weapons and vehicles. Find yourself an area rich with zombies and start slaughtering. Otherwise, this should come eventually through normal play (I unlocked it sometime in Chapter 2). At night you may find that the zombie density is higher, but they are also tougher to kill. Focus on vehicles at night, since you'll wear out your weapons on fewer melee kills.

Bridges between areas tend to be well populated and have plenty of room for driving back and forth. No matter how you kill zombies (vehicle, weapon, barehand, fire, etc) they count toward your total. Once you have killed 10,000 of the creepy buggers, the Achievement will unlock.