Sonic Screwdriver

The Sonic Screwdriver is a device used and invented by the Doctor. It has oodles of different functions, but the main use is to open doors. The Doctor has had many different versions of the Screwdriver, as described here.

Mark I
This was a simple rod with a light on the end. If the Doctor whacked a door with it, it would open. That was about it. The Daleks stole this device and the Doctor never bothered to retrieve it.

Mark II
Slightly more advanced, it could now be used as a scanner and had several other functions as well. It made a strange buzzing noise which irritated the Doctor, prompting him to change the sound on future models. This screwdriver was destroyed when the Doctor threw it at the TARDIS door in annoyance after the controls were overtaken by a strange force.

Mark III
Almost identical to Mark II other than obvious colour changes. This design is notable for being the first to incorporate a retractable nib for easy storage. It burnt out due to overuse and was deemed obsolete by the Doctor, who eventually replaced it after taking a lot of time to upgrade it. However, its shell was later given to his companion Romana, who rebuilt it a a sleeker model.

Mark IV
This model had many more functions, most notably being a remote activator for the TARDIS. It could also shatter glass and overload electronics, as well as being able to interfere with computers. This model blew up after being shot out of the Doctor's hand by a Sontaran, much to his annoyance. The War Doctor used the handle end to partially reconstruct it for a time, but it was rarely used as there was no room for pacifistic approach in the Time War.

Mark V
This sonic had a very organic appearance and had a blue light on the end. The Doctor used this screwdriver in much the same was as all the others, apart from the fact that it had a greatly upgraded interface meaning other people could use it. This sonic used a lot more than just sound waves and was a very multifunctional device. It was destroyed when the Doctor attempted to use it to overload an MRI scanner.

Mark VI
Almost identical to the Mark V, apart from the colour. It was used by the Doctor in his campaigns against the Cult of Skaro as well as many other aliens and monsters. This model was destroyed when one of the Doctor's regenerations damaged its core, and it blew up in his hands when he attempted to use it. However, It must have been partially rebuilt at some point because River Song (from the future) had a heavily upgraded version of this model which was apparently given to her by the Doctor.

Mark VII
After the destruction of the Mark VI, the TARDIS gave the Doctor a new screwdriver that was bronze and colour and had retractable claws surrounding a green emmitter. It had even more functions which allowed it to repair robots and remotely control starships, but it was destroyed after the top half was bitten off by a shark. Instead of replacing it, the Doctor simply repaired it.

The Trend
As soon as the League realised how useful the Doctor's Sonic Screwdriver was, Sonic devices became massively popular. Although none will ever be as good as the Doctor's own device, Sonic Devices were mass-produced and it became regulation that every member of the Human military should carry one. It is a true monument to peace that, in times of desperate need, Human soldiers would look not to their gun, but to their Sonic Screwdriver. The Doctor would certainly be proud.