Carry a torchlight? Nah, there is one on the phone, courtesy of the camera flash. The number of times I turned on the flash torchlight is just a few times.
In that few instances I have really used it, the camera area got really hot and I was worried of killing some of the electronics. One day I was in a discount store and picked up a cheap single AAA LED torchlight. It is too big to put on the key chain, but small enough to throw in the bag. Now if lighting is dim, especially deep inside the network rack, hit the switch! Keep it on as long as possible, and not worry about zapping my phone.