State Farm for 20+ years. Every few years we go for one of the "save 15%" pitches from one group or another and all we really ever get is a few dollars less per month for less coverage. Duh! I can do that with State Farm.
All in all we have been very happy with them, other than they have some agents who are gung-ho to drop you over anything and everything. Had the same policy with the same agent for almost 10 years, not even a ticket, let alone an accident, in all that time. My wife accidentally backs into someone in a parking lot. Less than $1000 damage, and they dropped us like a hot potato. Went to a different State Farm agent who reinstated our policy and gave us a break for the inconvenience. Other than that they have been pretty good to work with.