I've been playing with various LEDs all winter from bulbs to LED boards and checking with a light meter. I found these iBrightstar with a projector beam to be the simplest and brightest. They flash just fine without a resistor. Order them in red, clear LEDs tend to wash out the red lens too much.
https://www.amazon.com/gp/product/B0...1?ie=UTF8&th=1
