A_FireSTGrenade
From ZDoom Wiki
A_FireSTGrenade[(string missiletype)] (deprecated)
Fires a projectile (a Grenade by default) at a slight upward angle compared to the player's view. The following two lines are equivalent:
GRLG B 12 A_FireSTGrenade
GRLG B 12 A_FireCustomMissile ("Grenade", 0, true, 0, 0, 0, 6.328125)
While A_FireSTGrenade can be used with other projectiles, it is advised to instead use A_FireCustomMissile with the pitch parameter.