I know this is an old thread - but I do love a good martini. For my own martini, I prefer gin, and of the gin - probably my top 3: Bombay Sapphire, Gordon's (Yes, Gordon's), and Hendrick's (I'm surprised Kevin knows of it, not many do). I don't consider a vodka and vermouth a martini, it should just be called what it is, vodka and vermouth. Besides, if anybody gives you crap about drinking gin, tell them it's the original vodka, because it practically is - minus what it is fermented with, as vodka is usually potatoes or something while gin is juniper berries (which is what adorns the Gordon's bottle).
As far as shaking goes - I roll my shaker, I like mine 4 parts gin, 1 part vermouth - it rounds off the bite of gin and does not become too sweet. The reason you don't want to over ice it by shaking is because gin itself is an aromatic, if it's too cold, it simply does not taste like gin anymore. This is probably why James Bond drinks a vodka martini, as the taste of gin is something to be acquired. While we're on James Bond, have you ever had a Vesper? I tried to recreate my own, but Lillet Blanc is no longer produced and I didn't feel like buying any powdered quinine. It is however, a tasty drink if you have the alcohols to make it: 2 parts Gordon's, 1 part vodka (try using a 100 proof vodka, like Stolichnaya 100 - because it's probably the proof that James Bond during his times), 1 part Lillet, and a lemon peel twist.
Oh, and before I forget, another favorite of mine is the Manhattan, but I prefer it with Maker's Mark. It is basically a martini, but instead with whiskey and sweet vermouth (red vermouth, as opposed to the dry white vermouth) with a dash of bitters and a cherry. It is good stuff.
Happy drinking.