Behringer's Cable Tester CT100 is a very good cable tester.
It can accept XLR, mono and TRS phone ( 1 /4 ", 1 /8 ", TT), RCA and MIDI connectors. This device shows which input pin is connected to which output pin. This is a very convient feature when you are working in audio system with unknown cables. The continuity check allows you also so check if there is a bad connection: just put in the cable, press one button and wait of any LEDs indicating break kin connection shows up showing that there is a bad connection in the cable.
The tone generator functionality is a very useful in audio system testing on those case you need to have some signal generator. There are also LEDs to show the availability of phantom power presence.
I have found this device to be very useful. wel built and well worth of the money. Definetely the best audio cable tester in this price range.
Manufacturer home page: http://www.behringer.com/
Manufacturer product web page: http://www.behringer.com/CT100/index.cfm?lang=ENG
Price: 52 Euros (price information from http://www.thomann.de/ )
Product image (from product home page):
Ideas what would be nice to have in this device: I would like very much if this device had also built-in audio signal level (VU) meter, so this device could be used also to monitor audio signals on audio lines. This would save the trouble of having a separate signal level meter with me.