Flip-flop switch"/>
Here is another T-flip-flop variant.
Instructions:
This is what it looks like when it's activated:
You can see everything in the picture, the one block can also be swapped for a redstone block, or like me, just build a powered repeater, a gap and then a lamp. The repeater sends the signal through a block, behind which can be a redstone, which then forwards this signal.
Such a thing is really banal. Besides, there is only one variant here that really comes into question, namely the one from xxluke, because it is very space-saving.
There really are much better t-flip-flops out there.