Here is a solution that doesn't need triggers:
EDIT: this method allows you to throw your bombs at points. (AND NOT BECOME HOMING GRENADES THAT SEEK THEIR TARGET UNITS - WHICH DONT EXIST)
EDIT2: After reading the suggestions above, I note that they lack some part of the "throwin a grenade at you".
Acid Bomb HOMES IN on its target... Flame Strike just blows up the ground - it lacks a missile... etc.
The base ability is Pocket Factory.
Change the factory's duration to 0.01.
Change the Projectile Art to whatever you want your grenade to look like.
You can use any unit for a factory; any unit that has a model that has a suitable "death" animation (ex. unit with the Thunder Clap model).
Give the unit the "AoE Damage on Death" ability (see the abilities of the Goblin Land Mine).
What this will do is:
Launch the grenade, which will look like whatever model you specify in Projectile Art of the Pocket Factory-based ability;
Summon the unit when it lands - it will 'live' for only 0.01 seconds and promptly die, displaying its "death" animation (in the example above, thunder clap boom);
and the AoE damage on death ability of the summoned unit will damage enemies around it as it dies.
So: throw the bomb, it explodes, goes boom; people get hurt.