I always wonder why people have to behave like smartbutts when one of these topics come up. The whole "I like plutonium!!" thing is adorable, but while it could be considered an ontopic reply, the indirect questioning of the OP's intelligence is just annoying.
Same goes for "THERE IS ONLY X ELEMENTS BECAUSE I SAY SO" is also adorable but annoying. Whether something is considered an element depends mainly on the context. Like how the classical elements in western mythology is fire, water, air, earth (and spirit, if you are Wiccan), the Eastern elements are fire, water, earth, metal and wood. If anyone has a setting where element magic is present, it is common to find dark and light magic as well, and while some might say lava is either a sub element or a combination, any culture, real or fictional, could consider lava an element just fine, because it is, or is a part of, a force of nature. Like lightening. Or tsunamis. There could be an element of tsunamies if anyone cared to build up a proper fantasy culture about it.
Jeez. It's like trying to have a discussion like "Who is your fave deity?" and get replies like "There is no gods, only science!!!" and "Zeus is not a reeeeal deity, because [random nonsense]". It is annoying. Stop it.
That said, this is a pretty badly constructed thread anyway, since there is no kickoff for discussion (apparently just smartbuttery), which makes me sad, because elements for magic is an amazing topic if anyone would care to properly discuss it. But no.
One thing I can ask for is that you explain your bloody choice, so you don't end up spamming.
My favorite element? Nature, cause its made up of living things(science today cant do this)and its living creatures can get resistance against any other element in the world, only if, its absolutely necessary.
The only 'real' elements are the ones listed on the Periodic System of Elements. But even in the traditional, esoteric sense, I wouldn't call nature an element. Seriously, unless you revere Gaia or something like that you cannot possibly caterogize 'nature' as one element. Element! Elements are single pieces building up more complex stuff. Is there anything made up of several 'natures'?
I would have to say lightning because i know Physics and lightning is bad ***! As far as the Periodic Elements, I'd have to say Uranium because it is the element THAT KNOWS YOU'RE WATCHING IT!
As far as the Lightning/Fire debate, they are both a subset of Plasma (yes, like in Halo).
I don't know exactly how much rubber it would take, but by the time you were sufficiently grounded to resist a lightning bolt, you would be completely immobilized.