Chris Osgood comes to mind. At least from a regular season to playoff comparison. He was a pretty average goalie in the regular season, but has had quite a few nice playoff runs. He could have even won the Conn Smythe in 2008 and could have won it (if Detroit won the cup) in 09. The funny thing was that he was absolutely awful in the 08-09 regular season, then was beastly that playoffs, before going back to being awful again in the 09-10 regular season and retiring after 10-11. I know it could have just been a random happening, but it was pretty remarkable how he went from an .887 save percentage over 46 games in the 08-09 regular season, to a .926 save percentage in 23 games in the 09 playoffs. I figured with how poor he was that year, he might have them sunk in the first round that year.
Eh
He's only been past the first round one time though? Not that he was nearly the reason the Islanders didn't advance to round two in 2015 and he was injured in the second game of the 2012 playoffs. But if he's clutch, Mike Smith should probably be considered a clutch playoff goalie too. And Mike Smith's 2012 playoffs were a lot more than impressive than Halak's 2010 playoffs, but no one ever talks about it anymore.