Throwing any grenade with secondary fire somewhere upwards, while crouched, is bugged. When you throw it upwards in about 70-90 angle, it just rolls towards on the ground.
That's what it's supposed to do, it just rolls to the ground in front of you. If you're a hidden scout, this allows you to toss your grenades without revealing yourself.
Ah... looks weird though when you aim up and the nade spawns from your chest somewhere... k fail delete thread