Uses of the riot grenade?

[Eddie]

I just noticed that the riot grenade was changed to explode on impact, now they are way more useful!

And I also found a good target for them: reaper cavalry!
A direct hit has a good chance to kill. For a higher stun-and-not-kill chance throw the grenade next to the reaper. Two tiles distance won't kill but will not always down the reaper. The tile adjacent to the reaper has a low chance to kill and the reaper is assured to go down.

[peirceg]

Riot grenades are also good as you can pre-prime, but won't explode if you drop them! 

[netron]

Riot grenades are really great for taking out tougher enemies that you'd like to take out non-lethally, if possible. I usually use hallucinogen/knockout gas, but stronger enemies are often immune to choking damage. Also, IIRC, harpoon tranquilizers are 75 daze while Riot grenades are 72, against under armor however. In particular I've taken out some Marsec Colonial Marines(The guys in red armor with red shields in viper fighters) which were impervious to most of my other weaponry. In general trying riot grenades against tougher enemies that you'd like to take non-lethally has never been a bad idea for me.