For LED lights it was the Zebralight H50. Here's my first post on CPF:
"This forum convinced me to get the H50 when it came out, and now the 501.
Had to finally register to let you all know how grateful I am for the time you put into reviews and pics and everything else. You folks are great!"
Between the review from the user who was doing medical work in South America and all of the other posters' comments I had to have one. Sold my original to get a neutral version, still have the H50, H51, H501, etc..
My milestone on handhelds was getting up the nerve to buy an Ra Twisty. Wait,... this thread made me realize that I always come back to Zebralight and Ra/HDS... those 2 brands make up the bulk of my lights.
For lights in general it would have to be the 'ol Maglite 2xAA Minimag. I was in my teens when that wonderful light came out (~30 years ago), and it was a great lighting solution for the time. I've had many.