Ouchi Gari or major outer reaping throw is a great throw as a direct attack, as well as a setup throw into big throws such as seoi nage, harai goshi, osoto gari and uchimata.
Ouchi Gari is one of the original 40 throws of Kanos Kodokan judo, it is also part of the new revised 67 throws of the kodokan. It is part of the first set of throws in the Gokyo.
This throw is also effective in no GI grappling but obviosuly due to the fact that there is no GI to grip and manipulate, you must eith achieve double over or under hooks in order to fully control your opponent.
Below is a highlight reel of some effective Ouchi Garis in judo competitions.