High Energy - jtl3
A small selection of capacitors.
From L to R:
ICAR Bioenergy, Italy. 6uF, 2kV, polypropylene. 12 joules. Ultra low ESR & ESL.
Aerovox Energy Discharge. Defib. 224uF, 1.5kV. Castor Oil. 252 joules (!)
EPCOS polypropylene, 1.7kV, 10uF. Even lower ESR. Used for motor drive snubbing, etc. 14 joules. 
RIFA PEH200YX460BQ aluminum electrolytic. 6mF. 450vdc. 7 milliohms ESR. 607.5 joules. (For scale, a joule is the energy it takes to lift an apple 1 meter. A pair of these EPCOS capacitors could take a similar 100g object and lift it to a height of over a kilometer rather quickly if coupling was good.)

A small selection of capacitors.
From L to R:
ICAR Bioenergy, Italy. 6uF, 2kV, polypropylene. 12 joules. Ultra low ESR & ESL.
Aerovox Energy Discharge. Defib. 224uF, 1.5kV. Castor Oil. 252 joules (!)
EPCOS polypropylene, 1.7kV, 10uF. Even lower ESR. Used for motor drive snubbing, etc. 14 joules.
RIFA PEH200YX460BQ aluminum electrolytic. 6mF. 450vdc. 7 milliohms ESR. 607.5 joules. (For scale, a joule is the energy it takes to lift an apple 1 meter. A pair of these EPCOS capacitors could take a similar 100g object and lift it to a height of over a kilometer rather quickly if coupling was good.)