Whirlwind QBox
Anyone who's ever had to fix a complex sound issue without the right testing equipment can tell you, they'd rather have been golfing... in hades. Seriously, having the right testing gear isn't the best way to find dead cables and shorts - it's quite often the only way to figure out what's going on in a timely enough fashion that the show can go on... and the show (as we all know) MUST go on. That's why you'd be wise to pick up one of these bad boys: the Whirlwind Qbox audio-line tester.