I currently use the AVO Megger BM223.
It gives 3 ranges of Insulation testing and one of Continuity.
This meter has both an analouge and digital display.
It also has a Null feature for nulling out your test leads when doing resistance checks over long distances, such as when doing tests on the resistance of conductors back to the panel, from a fitting.
The BM223 is really only a dual use sort of instrument, as in sure it is good at Continuity testing and it is good as an Insulation Resistance tester, that may fit your bill.
But if I had the ultimate in testers, I would go with one of the Kyoritsu multi-testers.
I used one of these at an EC company I used to work for.
Things like RCD tester, Loop tester, Insulation Resistance, Earth Electrode Resistance and also a Phase sequence tester, makes these units value for money.
You can also download to a PC all of your test results and print them out with a USB interface.
Haven't we come so far guys!.