In New Vegas I talked a girl into killing her mom. Just typing that makes me feel bad.

Jumping off yoshi to save myself from missing the next platform. He was a good companion.

I failed to save Meryl in my first playthrough of Metal Gear: Solid.  I spent many hours trying to atone for that failure.  Killing Sniper Wolf made me feel really bad, too.  Wasn't able to bring myself to gun down the innocents at the airport in Modern Warfare 2.  Couldn't watch the Rachni Queen die in Mass Effect when I played the Renegade path on my second playthrough.  I play my games with a fully armed and operational conscience.

The first time I played GTA III.

In inFamous... I played through as evil Cole. I felt horrible and never did it again. People yelled at me, threw rocks; everyone hated me. And I killed them. Killed them all. 

I can't bring myself to do it again. Every time I start up the game and tell myself I'll be evil... I get to the first mission and fail. I can't do it. I can't do it.

Shadow of the Colloseus and Tales of Phantasia

when i was mean to morrigan ending our relationship :(. and when i killed that elf guy.

all in da:o

that is the best feeling anyone could have! i had it to, i killed them all, and i was happy, sticky grenades for the win!

Not only when I do something.....I really care about the people in the games =p..

As an example if in Halo I go in a tank and some A.I. soldiers sit on it and dies at some point I restart the mission...Or go to the last checkpoint X_X..

I want them to survive...Yeah I know it is crazy..Especially when I can them bring to a safe place but at the end of the game blow up the Halo (ring) while they are still on it X_X..

What? You can save her? Doesn't she always get tricturated by that machine? o.O