I'm renting a car in the US, cheap base rate, but, was unsure about the insurance add-on's I need. Usually I've taken them all due to confusion.

My opinion after a bit of research is that you should always take Loss damage waiver (LDW) and Supplemenatry Liability insurance (SLI) options. 

I discovered additional info too, such as LIS insurance which is always included by law but varies state-to-state and sometimes covers very little. 

My own travel insurance company were oddly clueless about US car rental insurance options. I'd have thought it is a common question.  I rang another company and got the info I needed though. 

And, don't get me started about Californias new child car seat laws!!