I don't know if any games have advanced grenade throwing mechanics yet. But here's an idea that will make the game feel more tactical.
Lets say you're in building. Your character is low on health, hiding in a room. Then, you suddenly hear footsteps from the hallway and it's getting louder with each step.
There are three ways to respond:
1: Make no sound and hope your enemy skips your room.
2: Peek out and fire your weapon at the enemy. You shot him first but you died because the enemy had more health.
3:The grenade wouldn't bounce very far, so you peek out and throw a grenade. You died before you could throw it.
You wouldn't use a grenade launcher, because your health is low, you don't know how far the enemy is in the hallway and the splash damage could kill you.
If there was advanced grenade throwing mechanics, your character would not have to risk peeking out of the room. Your character would throw the grenade sideways. And the enemy dies from the explosion, while your character took no damage because he's behind a wall.
In Battlefield 3 and 4, I've played conquest large on Operation metro and it's a big problem. Both teams are stuck in the middle of the map and it's very difficult to push. I've tried grenade bouncing, but that doesn't go very far, so no enemies died. If grenades could be thrown sideways, it'd be easier to push. As soon as I try to peek, I am exposed and literally 10 enemies are shooting at me. I'm dead.
For the magazine system.
If there are different variations of one specific caliber, I'd suggest the magazine system.
Lets say you have an inventory full of 5.56x45 ammo. 10 of them are armour piercing, 10 of then are standard, and 10 are tracers.
The idea is the mix all the ammo into one magazine. The mixing will be random but it should be customizable if done before game starts. For example when there are 10 or less bullets, tracers will occur more offten.
These are just suggestions. They are based off of the various shooter games I've played.