What pisses me off about Code Geass is how many loopholes there are in Lelouch's geass in particular. Like, I know plenty about loopholes, being a Java programmer, so I can't stand that he gets away without punishment for so many things. For example, when he quickly says "die" to people. He doesn't say when, where, how, if it's just them that dies, if it's suicide, homicide, or natural, etc. Everyone's going to die eventually, so the major loophole there could basically negate the geass, making the person live their normal life until, eventually, they do indeed die as Lelouch told them to.

Anyway, I'd want my geass to instantly show me others' weaknesses. Any type, I mean. Their weaknesses physically, mentally, romantically, and emotionally. The drawback would probably eventually be the fact that I would feel paranoia of my own weaknesses, maybe alienation, and not knowing how to gauge the weaknesses. Also, I'd want it to trigger at my whim, having to have the person in site, but no eye contact and no lack of control over when or how often I'd sense it.