5. Articulation. If we define articulation as the number of moving joints on a toy, then it perhaps comes last in terms of toy design. Children's toys are meant to spark imagination, and kids with a healthy imagination can do far more with a toy than the toy can do itself. Whether or not the toy can actually strike a dramatic pose, it will often do so in the child's eyes...especially a child doped up on sugar and caffeine.
The main benefits of articulation is that, despite the salute I just made to imagination, people generally like it when the toy most resembles the thing it represents. The more poseable the toy, the more likely it is to resemble the really cool robot on the package. Also, articulation is important for the adult collector because toys with high articulation make for mean shelf displays.
Most early G1 toys might be shiny, but they don't often make for the most dynamic dioramas. With G1, you were satisfied if the arms could hold weapons towards an oncoming enemy, and you counted yourself blessed by the plastic gods if the Transformer could bend at the shoulder AND elbow (see G1 Optimus and Soundwave). Vintage Transformers mostly used screws, nails, and pegs to create their limited swivel joints. Most modern Transformers come highly articulated: shoulders, elbows, hips, knees, feet, and even heads move all thanks to ball-joint technology or variations thereof.
Negative example: The worst offenders of articulation, however, were toys like the Throttlebots, Battlechargers, and Duocons--often toys with motors or spring-loaded features. The first two merely had flaps for arms that couldn't even be pointed forwards. I suppose they were forced to hipcheck any Decepticon that came their way. The Duocons (which were one robot that consisted of interlocking land and air vehicles) had arms that swiveled out to the sides, but couldn't point forward either.
I'm ranking articulation last of the five factors, however, because articulation is also a liability. Over time, joints wear out, leaving toys wobbly. Weebles might wobble without falling down, but the same cannot be said for their transforming robot cousins. As more joints are added, the less stable transformers become. Furthermore, every worn joint is also a liability for breakage. Fortunately, many of the ball-jointed transformers have more "give"--if something pops off, it can be popped back on. Alternatively, if something can pop off, it has a higher chance of getting misplaced.
Articulation, then, is the double-edged sword of toy design. It can make or literally break the figure.
Thoughts on articulation? Which Transformer do you think makes the best use of articulation? Which makes the worst? Let me know in the comments below!