While recorders with built-in microphones like those from Zoom are quite popular, I consider them badly-suited especially for video purposes. You definitely need the possibility to plug in decent external microphones, and then it's questionable if you will ever need any internal microphones at all.
If you can afford it and don't mind carrying the weight, get one of those professional field recorders like Tascam DR-680, Fostex FR2 or even a Nagra. They give you uncompromising high quality, reliable performance and good handling, for instance through well-operable gain controls. You also have multiple channels, which can be useful in a variety of situations.
If you appreciate low weight/size and affordable price (if only to be able to spend more on microphones, which can arguably contribute more to a good sound than any preamp/recorder), and only need 2 channels, I would recommend the M-Audio Microtrack II. It is really lightweight (and pretty cheap) and might still give you everything you need: professional mic preamps with phantom power (though only through ¼″ TRS rather than XLR, but fully-symmetric), and decent ADCs with 24 bit 96 kHz. You probably want 24 bit, because even with good analog gain pots you should always leave a bit headroom for field recordings unless you don't care if the limiter sometimes cuts away the dynamic range, and with a small recorder like the microtrack even more so as it's quite difficult to set the gain precisely. With that specific model you also have the drawback of a not consumer-exchangeable lithium battery, so you may need a portable USB power supply.