Technology..

Technology mainly to look gritty yet having a great impact:

-3D
-Old Film
-Final Cut Pro
-Amateur footage (off of a cam-corder or perhaps mobile phone) For e.g. films like the "Blair Witch Project" and "Cloverfield".
-High Definition

Films that look gritty yet are of a great impact are:
-"Requiem for a Dream"
-"Black and White"
-"Thirteen"
-"Lords of Dogtown"