I will vary my medium depending upon the Achilles Heel of the co-worker I need to intimidate, ermmm, communicate with. Afterall, the Office is a Battlefield, and communication is ammunition. You wouldn't go after a vampire with kryptonite or take on General Zod with with a clove of garlic, so don't make a similar mistake in real life. The choice is among three weapons, really: E-Mail, Phone, Face-to-Face.
Never let a Sales Guy get you on the phone: it's like bringing a sword to an Indiana Jones fight. You keep everything in e-mail for the Sales Guy; don't listen to the Sirens' Call!
There are always the "creative" types, or young punks who were raised online... these hipsters will weave e-mail rings around you. Nip their emoticon-laden shenanigans in the bud by marching down to their office or cube and having a face-to-face with them while standing a good six inches into their personal space. Grip their shoulder periodically. New Media-savvy hipsters hate having their shoulders gripped.
And be sure to phone the face-to-face time-wasters. These are often women, who will use (either intentionally or subconsciously) the insufficient volume of fabric in their skirts or blouses to achieve distraction and misdirection. Counter that cleavage with some Clausewitz, who said that "the third rule is never to waste time." So Scarlet Pimpernel her ass by avoiding any face-to-face while dive-bombing her voicemail box constantly and off-hours.
happy to help...