Audio-Technica Pro 45

Although this microphone is mainly for conferences, concerts with vocalists and so on, this a actually a pretty good bet if you intent on using it on a film set.

The very long cable (7,6 m/3 in) allows to avoid using (most of the time) another XLR cable to reach your recorder (the only hassle is to wind it (⊙＿⊙') ), and is easy to hide due to its small diameter. The pretty tiny size of it, in conjunction with the holder make it easy to conceal it near a fixed object or suspend it. Especially useful in a car to get a backup (with a bit of tape to hold the cable).

Sound is quite clear a moderate distance, and really usable for dialogues with little effort when you place it correctly.

Personally, it's always with me when I go on a film set or for an interview.