Which nut/washer combination to join timber to timber (joist to rafter)
The spikey washer needs to go between pieces of wood.   I doubt its usefulness, since the strength is either going to come from the bolt in shear, or friction between the wood surfaces, depending on how tightly it's bolted.  The teeth won't fix poor clamping.  

A lockwasher needs a lot of compression to function properly, it's really intended for metal.  If backing off is a concern, use the nylok or a second "jam" nut.  

You'll want large metal washers against the wood on both ends, otherwise the bolt heads will just sink into the wood when you try to torque it down.