"Monger" was once used as a verb, but it now is typically only employed as the second element of compound words. My OED says examples of such formations are "unlimited", with examples beginning in the 13th century: hay-mongers, holy-water mongers, insect-mongers (?) etc. The most familiar would likely be cheesemonger, costermonger (fruit/veggies), fishmonger, ironmonger, and whoremonger.
As the last-named example suggests, the OED notes that from the 16th century onward, the term nearly always carries the implication of a petty, disreputable, or comtemptible trade in the material - as in the modern "rumor-monger" "gossip-monger" and "scandal-monger."
Here is a costermonger:
...and there is a fearmonger at the end of this brief  video:
Reposted from 2008 to add this even-more-extreme political video -
- created by Winning Our Future (a SuperPAC). The video mixes homophobia and a generous dose of xenophobia into their apocalyptic vision. It has excellent production values and nicely defines "fearmongering."
Reposted again from 2012 to add yet another example:
Cartoon by Rob Rogers in the Pittsburgh Post-Gazette, via the political cartoon-laden Jobsanger.