Mortal Kombat (the original) (and on sega, cuz it had the blood code and SNES didnt) (a-b-a-c-a-b-b="get over here")
True Lies - SNES - This was probobly the game I played the most out of every game of that era, I remember all the cheat codes for that game too...
BGLVS - infinit lives
BGWPNS - all weapons
BGRLY - infinit ammo
MNCHT - Level select
Those codes from both games are forever burned in my brain and will never go away, I remember them better then my SS# and address lol
Also Secret of Mana - SNES
As far as Arcade games tho, nothing is cooler or more retro then the X-men Arcade game, that games was the tottal rock hard win, and I have never beat it. Almost did once, but ran out of quarters... remember when Arcade games actually took quarters? Do Arcades even exist anymore? 
As for video game Christmas memories... ask phluff about the time I got an N64 for christmas.
It was almost as bad as the N64 kid, no joke.