Funny, to me personally the Marauder was the opposite of a sleeper - looked and sounded meaner than it really was (I'll catch some gas for it but honestly to some extent so was the '94-96 Impy SS). The 4.6 DOHC was not ideal for a heavy car, no low end and was a rev'er - but a blower goes a long way. Again both the Marauder and Impala looked good, but really in stock form weren't very quick.
Regal GS I can somewhat agree with, again it's really not fast in a straight line but it is an excellent handling and braking car. Either CD or MT gave it the "Best Handling FWD" nod for 2012. I greatly enjoyed mine, would've been about perfect with about 350hp and AWD.
SHOs are definite sleepers and with a tune (such as our friends at Livernois) they run well into the 12s, and AWD is always a strong advantage on the street.
2016 Chevy SS HW - can, Rotofab, 1-7/8 ARH headers +cats and LMS tune
2001 Trans Am NHRA Edition - TSP built Darton sleeved 454 and a lot of other stuff