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.
1/26 - Inquisition w/ Truckfighters
1/29 - Alcest w/ The Body
2/11 - Marduk w/ Incantation
2/16 - Pain of Salvation