Here are the symbols for the three most liquid Ultra ETFs:

NASDAQ 100: (QLD) [2x long]; (QID) [2x short]

S&P 500: (SSO) [2x long]; (SDS) [2x short]

Dow 30: (DDM) [2x long]; (DXD_ [2x short]

TWM ULTRASHORT RUSSELL2000 PROSHARES