During the mission "Anything for Trish", you will be on a bus Trish is driving from the Neon district to the Warrens. The bus seems to emit unlimited electricity from the top, so if you simply stand on it your energy will refill no matter what you use (sticky bombs, focused shot, etc). There are also plenty of baddies looking to take out the bus, so you have ample supply of take downs available for this trophy.
Questions, corrections and neg vote justifications below.