Let's back up a bit...wiring harness basics?

[Critter]

I am still on the fence about whether to re-work my original harness or send it off to someone. I am a pretty good DIYer with an electricians background so circuits and wiring are nothing new to me. My question is this, for your regular run-of-the-mill LSx swap, what sensors or connectors are needed? Obviously, I know about the major ones, but some seam to be in a grey area and that is very confusing to a person in my situation. Another way of looking at it is, how many connectors should be on a re-worked harness. Maybe we can keep the answers in somewhat of a specific formula...

Connector/Sensor Name, Required/Suggested for best results, Needed for emission, Needed for auto tranny

I'll start with an obvious one...

Throttle position sensor, required, all, all tranny setups

Hopefully this makes some sense. I have been looking for this info all over the web and nobody has it listed this clearly. Please help me fill in these blanks.