The TFC Frag Grenade uses the Half-Life 1 Grenade's ground model, which itself is a Mk 2 frag grenade.Despite being labeled a Fragmentation Grenade, the Frag Grenade does not release shrapnel when it explodes the damage done by it is purely based on the explosion of the grenade.In addition, TFC Frag Grenades make a very loud noise when they explode, which tells enemies to avoid going near the loud explosion, much like QWTF's "ping-ping" sounds. In TFC, the Frag Grenade is distinctive enough that an enemy will be able to notice it bouncing across the floor and avoid it. In QWTF, the Frag Grenade makes a distinct "ping-ping" sound when it bounces on the floor, which tells enemies that somebody is spamming grenades nearby and that they should avoid nearby areas until there are no more "Ping-ping" sounds. If you attempt to spam Frag Grenades in maps where it is unnecessary, you'll find that enemies will easily be able to avoid them. However, there are some maps, such as Dustbowl, where spamming grenades is an essential way to either deny the enemy the ability to move forward or to push back enemy defenses. The grenade can also be used for spamming, but this is generally considered a waste of a grenade, especially if you don't prime it before you release it. This takes some degree to prediction, so try to see how your target follows a movement pattern before you begin priming the grenade. If it is possible, try to make it so that the grenade intercepts the target's movement path so that he will be very close or right next to the grenade when it explodes.
If done correctly, the target will suffer major damage or be killed, depending on much health and Armor he had before the grenade exploded. Make sure to move away from the target so that you don't get caught in the grenade's splash damage.
To do this, prime the grenade, then throw it at the target about one to two seconds (depending on the distance between you and the target) before it explodes.
The Frag Grenade should be used to either further inflict damage on a target or turns the odds in your favour when you're deathmatching an enemy.