I suspect if you took everyone at this forum who has spliced a cable over #4 and counted the number of jobs in total I would still have done more.
I have splice everything from #14 to 500 MCM ( also coax, fiber and com cables ) .
I splice 12 volt and I splice 13,800 volt.
I have used cold shrinks, tape kits, pour kits and torpedose ( and I even do the old style tech in pipe splice for kicks to keep people guessing )
If your going to splice anything that draws power use a proper compression link and the proper tool. Copper on Copper no dissimilar metals. Avoid mechanical fittings ( split bolts ) they eventualy loosen. And Finaly pour it in epoxy if its going to get wet.....
I do this for a living I used to splice so many cables in a night I was questioned on it ( hey not my fault people break stuff I just fix it ). The main thing to rememeber is you must use the right material for the aplication.
There are a lot of people here sugesting things I don't like and simply would not accept in a job for safety and reliability reasons.
I will confess to using a few of these tape kits over the years
http://www.plymouthrubber.com/These are generaly good but I have had a few get wet and fail. My fix for that is the Raytec host shrink kit over top of the plymouth tape kit. Plymouth makes some of the best tapes I have ever used. I am particularly fond of the 153 vinyl and outer jacket repair tape with mastic.
My worst fear is one of my splices or repairs will fail and someone will get hurt. This has never happened to me but I have seen it happen.
I take about 45 minuts to do a realy good " million dollar splice " as the miners call it. Some clowns do it in 15 minuts and I will eventualy find them and replace them or will be called because a poor splice has failed.