See I personally think that one of the greatest parts of any RP system is the fact that you get to be someone you're not. Of course no matter how good an RP'er you are some of your personality leaks into a character, but being able to be "evil" in an environment where there are no real casualties and no one really gets hurt can be incredibly fun. I've had players who out of game are saints of kindness and generosity play characters that were unmitigated bastards.
The most recent example I can think of was in the last DH session of a campaign I've been running the PC's got stuck on a ship in the warp with a rogue eversor assassin on it. This thing was WAY more powerful than them and had been cutting a swath through everything they and the NPC guards could throw at it. The one thing that had slowed it down at all was when the pc's purposfully traveled through populated parts of the ship as it followed them as it would stop to kill every living thing on it's path between it and them. As they started taking wounds and running out of resources they had to find more and more crew/passengers to keep between them and it to have time to plan and reload/recover.
The finale of this whole session will probably live on in infamy for being one of the biggest ******* moves I've ever seen a PC do. They had tried using grenades on this thing before and even tripwired explosives, but every time they had it had either been too fast and avoided them or too perceptive and disabled them. So using the knowledge that it would stop and kill anything alive and that they were running out of people to slow it down with they strapped a bunch of explosives to some hapless passenger and shoved him out into the hallway with the assassin who promptly spent his turn cutting the guy down and then dying in the resulting explosion. The PC to formulate this plan is the biggest hippy love/peace vegan pansy I've ever met. Your in game decisions are just that, what your character would do, not what you'd do in real life.