You guys are making me remember things... My favorite tactic was throwing flashbangs through the twin double doors on Dust2's Long A route when I heard Ts coming through. Except one time all I had was an HE and a pistol against rifle-wielding Ts, so I hid in the pit and chucked it when they came through.
It nailed a T in the head and killed him instantly. Not the explosion, the concussion of the HE hitting his skull.
I died too shortly after, but the T and I were laughing our butts off anyway.