K-Boom is a type of explosive developed by Bean the Dynamite. The chief of security planted two of these bombs around his casino as part of his plan to film an "epic". The detonator was given to The Dice, a member of The Family who held the casino to ransom, urging the owners to find the bombs before he bankrupted them.
Sonic the Hedgehog found them both but could only disarm one (with help from Porker Lewis). The other's explosion (detonated because Tails couldn't stop winning at Blacksnap) was contained in a vortex by Sonic.
Bean favours these explosives as they are small, compact and reliable - "the perfect weapon".