insted of having dedonate on impact it will rebound a bit or just delay the the dedonation, that will make it more usable in some circumstances.
an interesting idea. could be useful for clearing chokepoints around corners. or firing from behind cover.
that could maybe an ammo type... It would probably need to lose its direct damage, but that means it could maybe do some more splash damage. The major problem is the chance it hits and enemy and bounces away at a weird angle like normal grenades, but even a normal grenade would be an interesting option for the thumper.
Or to create chokepoints by firing before attackers can get into position to use the Thumper against you, which also prevents enemies from gathering nearby and forces them to take damage even before they cross the chokepoint. Seems to me it would be a bigger boon for the holders of the choke than those trying to breach it.
