Indeed. Hence why I have to withhold information. I at least try to drop hints, but if I had to write within the knowledge of my character, I'd also not want to drop hints because they could be used to discover my ruses, which is usually something I want to keep hidden. Mainly I don't want to just "give" people solutions to defeating or others coming out on top of my characters. While most of my characters are dirty fighters who'd cheat in IC (Such as having a hacker in Virtual Reality Game RP's), I myself try not to cheat in a narrative sense. I shouldn't have to tell you how you kill my characters; sure my dude is an amorphous blob, but shooting him is still going to do damage. Might not kill him the first time, but that doesn't mean pumping him with more bullet's won't hurt.

A sort of snide joke I make when I have to make characters with weaknesses is putting in "Getting stabbed to death" or "Riddled with bullets". You know, logical weaknesses.