ryuu ga waga teki wo kurau

That shit Hanzo's saying when he ults
(Most of the times ending with him getting Play Of The Game)

This is a famous quote of Hanzo you can hear in Blizzard games like Overwatch and Heroes of the storm.
It literally means: "Dragon, consume my enemies!". In Japanese: 竜が我が敵を食らう

Overwatch explanation:
This is the last words you will probably hear from the angry enemy asian with bow before dead, if you will not run quickly from his sight. Sometimes it is impossible to guess what area will be under this effect, because it can go through walls. It works the most efficient way in combinations with control effects, for example, Zarya ultimate.
Important thing: if enemy Hanzo uses ultimate, you hear Japanese version of this quote. Otherwise, if is used by ally, you hear english version, so it is unnesessary to try to avoid it.

Heroes of the storm explanation:
In heroes of the storm it works the same way, but it is much less dangerous and deals much less damage. Usually, other ult, "dragon's arrow", is considered to be more suitable and it can be used for escape, stun, finishing, interrupting, etc. On the other hand, this ult can be combined with powerfull stuns, for example, E.T.C. mosh ultimate. Also, this ult is one of the best area control ultimates.
Nice thing: you can easily eliminate Abathur with this ult, if he won't wake up in time and get out of it's effect's area.