HC stands for hydrocopper and are components with waterblocks pre-installed at the EVGA factory.
The acronym FTW stands for "For the win". FTW model graphics cards come with a higher clock speed and are more likely to overclock further than a reference card. Each card is hand tested and guaranteed stable at the advertised clock speeds.
SSC stands for super-super clocked and is one below FTW. This means the card is factory overclocked by EVGA and has been tested for stability at the overclocked clocks.
SC stands for super clocked. It is the lowest overclock EVGA offers but is still tested and guaranteed stable at the advertised speed.