Most likely Combat. Loved that bounce-the-shots-off-the-walls mode. Then later on we got Space Invaders, and the whole family gathered around the 21" playing round robin. Good times.
My brother is gaming, he's got a PS2 and an Xbox, and my mom plays card games and stuff on the PC. When my folks come up to visit, I usually get my dad to play Ratchet and Clank, Hot Shots Golf, or Katamari Damacy together. Last time we actually played Neo Contra. Not necessarily his type of game, but we had fun [and thank goodness for unlimited continues on Easy mode, we died like seven million times].