Age of Mythology has an O CANADA cheat. It summons lazer bear, an incredibly powerful unit with a maple leaf cape that shoots laser beams out of his eyes. He even comes with a couple other little forest critters who cheer him on as his lasery gaze vaporizes your enemies.

Heroes of Might and Magic II and III cheats. Unlimited movement in II ("coconuts": I think?) was the best. It felt so rewarding to replay a difficult map you all ready conquered; replay it again with this cheat and walk right over to the bad guy on day 1 ftw!!!

Cheats are most rewarding to mess with after you all ready earned it by beating the game IMO.

I know this answer, easy:

Age of Empires II cheats:

lumberjack, cheese steak jimmy's, rock on, robin hood (1000 wood, food, rock and gold)
how do you turn this on (crazy killer Viper car)

I knew those cheats offhand any day, and boy did I use them when I wasn't so good at AoE.

show me the money!

"Weldersbench" on conquers bad fur day, was great for when you had mates over and play "It's war"... good times.

That has to be in James Bond:Nightfire. The one player was so boring I just couldn't play it, but the mulitplayer, was well, played for more than 100 hours. I used a cheat to not have to do the single player. That's really it for me...