Who is your favourite Teenage Mutant Ninja Turtle?...

Leo because he wasn't a caricature. Also, he was always the most balanced in the video games so I'd either start with him or save him until last for harder stages.

1. Leo
2. Don
3. Raph
4. Mikey

The very first Turtles action figure that I got as a kid was of Master Splinter, but the first Turtle figure was the wacky spinning (on the ground) Leonardo model, which was pretty cool, for a short time before something either broke of or became damaged, which was sadly happening a lot of the times, but super-glue could do wonders back then. And since he was the first real Turtles action figure I owned, he became for a short period my favorite, but also through watching the cartoon show on TV.
However, not long afterwards I began reading the TMNT Adventures comics which at first seemed to be pretty much taking the story straight out of the highly popular cartoon show and into the comic books, but suddenly around 10-15 releases, it all changed style and began to ditch the stories revoling the show in favor of brand new stories and characters, and this is where I really started to love the Turtles, as I enjoyed that the comics took on a whole different route and journey that the more kid friendly show. 

Suddenly topics and themes such as history, religion, war and science all become heavily involved into the monthly Turtles adventures comics and I noticed that each of the four Turtle brothers had far more of a "story" or depth to them than the TV show, and Raphael for me stood out the most in this case.
He was not the wise-cracking idiot but one who seemed more out of touch with his inner anger and his darker sides, but as the comic went on he met up with the female ninja warrior Ninjara aka Umeko and I loved how their relationship really got on and sadly as the years went on by, they ended rather badly but it was something completely different than most of the Turtles stories I had seen/read earlier and it felt much more "mature" in a way.
Anyway, my favorite Raphael "version" is the one introduced in the epic (my favorite Turtles comic) The Future Shark Trilogy which shows us a possible future not that far ahead, in which most of the world is in ruins and lies under water, and here some of the coolest and darkest villains return for a classic showdown, that and the story of the future turtles, and how the world as we know it pretty much gets screwed up.

To cut a long story short, Raphael have been my favorite turtles since I was 6 years old. 
I had 8-10 different Raphael action figures, I tried to make my own sai knives at school, which did not go down that well with my teacher and when he hooked up with Ninjara, I was so happy for him to be the first of his brothers to get a girlfriend, and I hated that they kept making all kind of crappy and uneeded Turtles action figures, but never made one for Ninjara who had become such a vital part of the gang during most of the Adventures run.
All in all, Raphael, no matter version is my favorite.
During the movies I would pick the 1990 one, which I thought was the best that I have seen as of now, perfectly combining the darker/angrier side to the more vulnerable and yet sometimes jealous but also over-protective one and for me I doubt that I will ever see such a great movie version ever again as the one in the first motion picture.

Another important late-20th-century TV series I haven't seen. I really need to check out shows of these great shows. 

Michelangelo.