@scott - DAT is a Digital Audio Tape.
This is the model I have. It's basically a heavy Walkman that has an XLR input with Phantom power, a rechargable battery and stores audio on what looks like a BetaMAX tape but is really made for digital audio. You can find them for about $400-$1000 depending on the model. It's an expensive tool, but for a sound designer, it's priceless.
These models are giving way to portable units that record directly to WAV. They use WAV because it's lossless. I've seen some people carry a 12" Macbook and a firewire powered audio interface into the field to record sounds. You use what is comfortable for you.
@psYco - Voice acting is not really that bad to do for a demo/proof of concept. Sound quality is not your issue there, it's the quality of the person's acting. You can stick all the effects on it in the world, but you can't change the person's personality. Game publishers will let an independent developer get by with decent acting in your proposal demo. If they accept you and give you a budget, then you hire a real actor to do the work. Voice actors are going to ask for a script and design doc in advance so they can work on their delivery. Just be sure they sign an NDA before you hand any of your IP over to them.