Posi-Products™ Wire Connectors
Crutchfield Customer Review (What's this?)
These are the best! A very clever product. Very solid contacts, very easy I to use Buy extras because you will never want to go back to the old kind.
Pros: Very easy installation. Makes contact through a single small hole in insullation. Almost self-healing when removed. A tiny drop of silicone would make it completely sealed upon removal.
Cons: Better instructions as to strip length of tapping wire would be nice. It took a couple tries at first to figure out best length. Once that's figured out, they are a breeze to use.