Aviation reporter Bill Sweetman claimed in 2013 that the classified, stealthy, unmanned intelligence, surveillance, and reconnaissance (ISR) platform being produced by Northrop Grumman was designated RQ-180. I asked him about this because it didn't make any sense to me (there was a logic to the Lockheed Martin RQ-170 designation that didn't apply to the NGC platform). Bill insisted that a source had specifically referred to the new plane as the RQ-180. I still remain skeptical.
Unclassified USAF briefing materials from 2009 and 2010 refer to it variously as MQ-L/O (multi-mission, unmanned, low-observable) and Penetrating-ISR or P-ISR. One source told a reporter from Aviation Week & Space Technology that it was the "RQ-XXX," though he may have been self-censoring the number. Frankly, I would expect it to have an MQ designation because it likely has at least some offensive capabilities (EW/EA and/or SDB delivery?). Much about the platform remains highly speculative.