ShellShock Live

You really just have to get lucky with this one. Setting the obstacles to High in the settings helps, but you really just have to pray that all 3 are on the map at once. You can use a flair weapon like air strike, just make sure that the flair hits all 3 before dealing damage. Other good weapons to try this with include bounstrike, homing missile, grenade storm, nuke, roller, back roller, and dead weight. Going into a FFA 8 player lobby can help with this as well.