Mount & Blade: Warband

it doesn't matter what throwing weapon you use as long as you get the kill on horseback. You can jump into any empty lobby with a friend and take them out for an easy if lengthy grind. This is very difficult to do legit as hitting people on foot is hard enough let alone riding around on a horse. Players that see you can very easily dodge your projectiles and kill your horse while you make passes. Your best bet is to creep up on players switching their loadouts or that are distracted by other players. Aiming in first person is also a lot easier with accuracy so take it slow and try to lead your shots.

The Khanate faction is best for this as it has a very viable mounter archer class. If you can't find a server with Khanate then try and vote for some map and choose it as a faction. You can use any projectile but I would recommend not using the crossbow at all. Mounted archer can be very hard to play at first, but with practice and perseverance you can actually perform very well and consistently, even on controller. I preferred third person but I know most people prefer first person. You can boost this with a friend in an empty lobby but honestly I found it so fun I just did it normally.