Hmmmm. Just off the top of my head:
Omaha Beach from Medal of Honor: Allied Assault. Will always be awesome.
The Heat-inspired bank heist mission from GTAIV. Makes me super excited for the heists in V.
As far as bosses go, pretty much all of Dark Souls.
07/24 - Mutilation Rites
07/25 - Masked Intruder
07/27 - Touche Amore
07/31 - Warped
08/01 - Cannabis Corpse