in pvt the Sase from this daily build is one of my absolute favorite, it requires a bit more micro now that widow mines are a threat but its still very strong and transitions you well into a later game, http://day9.tv/d/Day9/day9-daily-468-huk-and-sase-fantastic-pvt-openings/
in pvz the immortal sentry push is quite strong but I also really like going for a +1 4gate timing off two base in order to do economic damage at their third http://wiki.teamliquid.net/starcraft2/4_Gate_%2B1_Zealot_Pressure_(vs._Zerg) again this does damage while still transitioning into a longer game.
pvp is hard to recommend a specific build for because it has so much variance especially in hots but the daily that prometheus recommends is really good.
Generally the idea in all good pressure attacks is to insure a strong economic transition behind it. 4 gates, immmortals and a warp prism off of one base its a huge investment and if that attack fails you are basically dead. Its generally better to execute slightly less costly early aggression that is not aimed to kill your opponent outright but rather aims to but them in an extremely unfavorable economic position thus sending you into the mid or late game with a comfortable lead.