I had thought about for a special mission giving one of my blood angel terminators a few frag grenades and thought about these following rules
1. a frag grenade can only be tossed 5 spaces
2. A marine may toss a frag but may not move afterwards or take any action afterwards, A selected marine must also not make any action such as movement or shooting if he wishes to use a frag grenade.
4. Frag bounce! if a marine is directly at corner of a junction a marine player that meets above criteria for using frags may choose to chuck the grenade around the corner. on a rule of even number the marines succeeds on lobbing the frag around corner and grenade may placed four paces around corner. note only can be done if marine is at corner if marine is one space back from corner space frag bounce cannot be done. if player rolls odd number then gernade toss fails and marine fumbles the toss and grenade lands on space on other side of corner and explodes. since marine is at corner the wall blocks him from blast but any marines caught in blast radius must make a save role.
5. if marine with grenades is killed a fellow marine may pick them up from his body by spending 1 action point.