I think most non-industrial electricians can get by with the following 3 test instruments:

1) A non-contact voltage tester

2) A solenoidal tester with a continuity feature, like the Ideal VolCon. This tester is as important as a linesmans pliers and a t-stripper.

3) A basic clamp around ammeter that incorporates a DMM, like Amprobe's ACD-10.

If I were to recommend against any one type of tester, it would be the digital "wiggy" type testers because they are suseptible to ghost voltages.

Peter