They might however have been able to produce "dirty" bombs. These are bombs with conventional explosives that have enough radioactive material in them to cause radiation sickness to people in the blast area, and leave the target contaminated for some time. However, there was little understanding of the long term effects of radiation at the time, so it is unlikely the Germans would have thought this to be an worth while approach.
One thing the Germans did have, but never used, was Nerve Gas. The allies did not even know there was such a thing till after the war. Had the Germans used it, the allies would have had no defense.