Anyone remember the Champions of Norrath games for the PS2? (I'm pretty sure those games existed for the sole purpose of allowing players to create and level new characters for that Everquest game, but they did have their own standalone campaigns as well.)
I can't remember exactly how it went, but in the first CoN game, there was a glitch in the character creation menu that could give you near-infinite skill points. What you did was, basically, select a race (elf, barbarian etc) OTHER than the one you wanted, allot the skill points in a certain manner - then deselect that character, choose a new one - and you'd get to keep the skill points from the previous one as well!
AND the process was repeatable.
You had to keep from getting too greedy, though - the game wouldn't let you move past character creation until all skill points were allotted, and each skill only went to 99, so it was entirely possible to aquire too many points - and be stuck!
A couple of more modern examples (both from Saints Row 2
If you go cruising through the sewer tunnels below Stilwater, vehicles intended to spawn on the parking lots above will sometimes appear down in the tunnels with you. This almost never happens, which is what makes it so cool - you don't see it often enough that you ever really come to expect it. Each incident is a surprise. The really strange thing is, though, that whenever it DOES happen, the vehicle will almost always be a motor home!
Also, I don't know if this really counts since I've only had it happen once, but you know that early mission where you have to recruit Shaundi? And impress her by hitting a few jumps with her car? Well, one time when I missed that jump over the canal, the car sort of clipped into the wall, my character went flying through the windshield - and promptly died. Somehow, she was also catapulted miles away. Next thing I know, I'm looking at a "wasted" - screen which shows her as a Team Rocket-style speck in the sky! I've no idea what the hell happened, but it was SO worth the hospital fee!
On that note, I'm definitely going to boot up GTA IV tomorrow and look for a swingset! Thanks for the tip, guys!