For pvz, french (bagguette) style is very popular right now http://www.teamliquid.net/forum/sc2-strategy/481008-french-pvz-guide
For pvt I'm not really sure, but I think something like blink into robo is good. You need to make sure you have detection for the inevitable mine drop.
pvp there are a lot of viable openers. oracles, blink, robo, phoenix, dt, dt-robo, 3 gate all in, and probably more. It entirely depends on personal preference and maps.