For many years, observers have noted the existence of a number of tremendous outburst amplitude dwarf novae. We present a summary of the known observational parameters for these exceptional systems. They show outburst amplitudes of 6-10 mag, have rare outbursts (interoutburst times being months to decades), and only seem to exist in dwarf novae with short orbital periods. We calculate new accretion disk models which can reproduce their outburst behavior very well. It appears that these dwarf novae have low mass transfer rates at minimum, and the viscosity during quiescence is about 10 times smaller than for other dwarf novae. Their relation to SU UMa stars is discussed.