The soldering iron I am going to vote for is one of the worse soldering irons ever, but also one of the most fun.
When I was at school, one of the popular soldering irons was the Scope irons, and amazingly, it still seems to be available today.
The original "SuperScope" soldering iron was 150W and then they brought out the "precision" 70W model.
They had temperature control - your finger. When you pushed a ring or level on the smaller iron, it pushed a carbon electrode onto the unplated copper tip. The other end was connected to a 3.3volt 50A transformer. Instant heat! If you held the finger down too long, the tip started glowing red, and since it was an unplated copper tip, you had to keep plenty of spare tips and electrodes.
You had to learn by feel when the temperature was about right, and admittedly there were lots of wrecked phenolic PCBs along the way. Why it was fun is you instantly had so much heat available. Soldering to groundplanes, to bare metal - it was just so easy. You did get good at keeping the temperature about right with practice and it was far superior to any of the unregulated mains powered alternatives of the time.
Other then the feeling of pure power, it was fun as the 3.3V transformer was pretty indestructible, and I had a great time seeing what 3.3V @ 50A could do to bits of wire and anything else at hand.
If anyone is crazy, here is the link to buy this 50 year old marvel of Ozzy technology. Must be a really great design to last that long!
http://www.ozautoelectrics.com/scope.htmlMy major disappointment is that the original Ferguson transformer has now been replaced with a wimpy-looking plastic encased job.
Richard.