There are lots of attacks which are on reduced block ciphers. There are practical attack on five rounds of AES-128five rounds aes broken in six minutes. I was just wondering if there is any practical application of reduced rounds of AES where less than 10 rounds are used.
There is not much use for reduced-round AES as a block cipher per se. AES has been carefully designed to provide appropriate security margins and 20 years of cryptanalysis show that they are just right - reducing the number of rounds would make it potentially susceptible to attacks.
On the other hand, the single round function is a very useful transformation that provides good mixing and other provable properties. Moreover, widespread hardware support for the round function (like AES-NI instructions and similar) makes it attractive from the performance point of view.
A good example is a lightweight hash Haraka designed for short-input hashing that uses AES round function.