Beaming as such should suffice for that: conventional hand grenades would in fact be much better payloads than giant antimatter bombs, as the foe could strike with impunity without having to consider his personal safety or other complications. Remember "Visionary" where the Klingon agents used a replicator as a transporter to place an eavesdropping device? Doing that with a hand grenade would be nasty. (Alternately, you could just beam out the heart of your target.)
Transporting is blocked by shields, though, and that's enough to stop the weaponization of the technology. If you can defeat shields, you don't have to bother with transporters in the first place.
But there should be no limit on what can be transported, because we have already seen it all. Antimatter, pff. How about creatures of pure energy?