RS Ophiuchi is one of the most famous of the recurrent novae, and AAVSO observers have been following this star since at least 1914. It even got a mention in Leslie Peltier's memoir Starlight Nights (page 192 of the Harper & Row edition). The first recorded outburst was in 1898, while the first outburst observed by AAVSO observers occurred in 1933 (Peltier, 6.4 on JD 2427300.7 although it was discovered independently by another observer several days earlier). RS Oph has been caught in outburst four times since, all at irregular intervals from the preceding one. These nova outbursts appear as a brightening of nearly 10 magnitudes that fades over the course of about 100 days.
Outside of outbursts, RS Oph exhibits some of the same characteristics of the symbiotic stars, and it's possible that the physical mechanism for the large nova outbursts is similar (but much larger in amplitude) than typical symbiotic star outbursts.