Player > Feats > Pull the Pin
You can activate a foe’s grenade.
Improved Combat Maneuver (disarm).
When you make a successful disarm combat maneuver against a foe that you know has grenades, rather than disarming the foe of a weapon, you can activate one grenade in the foe’s possession. You can activate only a grenade that is ready to be drawn and thrown (not, for example, a grenade stowed away within an equipment pack). The grenade explodes at the end of your current turn, unless it has a delayed fuse that causes it to go off 1 round or more after it is activated.
The foe takes a –2 penalty to the saving throw against this grenade, and the grenade’s explosion has half its normal area.