Today Toucan brought up the subject of cosplay weapons and how to register them with Comic-Con security. On that note, it's worth talking about security guards in general. We'll start with a positive caveat: most security guards around the convention center are pleasant people with benevolent intentions. And I think we can all admit their job isn't terribly exciting or enjoyable, since they have to put up with our annoying questions, check badge after badge, and catch rogue Con criminals slipping through alternate entrances. (Yes, that happens - I once saw an unbadged woman dressed as Pocahontas come up the outside staircase and convince someone to let her in an unguarded door. She was apprehended in under a minute.)
So rule #1 for dealing with a security guard is to be nice to them, even if they're acting like a pompous ass. Because that does happen sometimes. The thing is, they may be behaving unfairly and you may be in the right - but telling them off will not get you where you want to go. A few years back, Rhys Ifans was charged with battery after an altercation with a security guard. He's a semi-celebrity, so imagine how it'll go for you as a regular attendee.
If they're asking for your ID, show it. If one security guard told you something (yes, you can leave this panel to hit the restroom) and another one doesn't want to let back into the room, be patient and explain as credibly as you can. I've always been able to talk my way back into things when this has happened, but lots of people haven't. (These days you'll usually get a special bracelet or ticket to visit a restroom.) Do not condescend or shout, or make fun of their hourly wage. I know it's tempting, but it won't accomplish your objective and can escalate in a way that sucks only for you.
Don't assume security guards know where panels or even rooms are. Sometimes they'll just give you random answers because they're completely indifferent to your Con satisfaction and want you to go away. Often they have no idea whether your spot in line will get you into the room, or they'll leave a line of people waiting instead of bothering to announce that a room is full. Again, most are respectful and friendly. But you will occasionally run into one who isn't.
Generally speaking, they're there to enforce safety rules, not supply content information. But sometimes they can't even agree on that. I was in a line last summer involving multiple guards from different companies disagreeing on where we could stand, if we could wait, etc. Some would yell at us, others would welcome us, some would force us to leave the line and then a new guard would let new people form a line. In this case, the best thing to do is point at someone, say, "But that guard told us we could" and sow seeds of uncertainty. Send a friend to get a new security guard in a different kind of uniform and plead your case. The time-honored art of playing one person against another is effective for a reason. Also - if you ask a security guard for a special favor and they say sure, ask if they can give you a ticket or physical indication indicating that special dispensation. Otherwise you have only a story to give the next guard who asks what the hell you think you're doing.
If you want to complain to a security guard about something, don't expect much. Most have good intentions but they don't have much real power. If you get harassed, remember you're in a massive crowd and descriptions aren't of much use, so try to read the person's name off their badge. That will help security actually do something. That said, most attendees are very polite and helpful with each other. Despite how crowded and frustrating things can get, there's always a strong spirit of camaraderie at the Con. And things like cutting in line are policed quite swiftly and effectively by the crowd.
All in all, you get the idea: don't antagonize people with the power to bounce you out of the convention center. Suck it up, appear deferential and honest, and flatter/charm them if you can do it convincingly. If one pisses you off, let it roll off your back. Odds are that won't happen, but it's really not worth fixating on if it does. There are too many good things to spend your energy on at Comic-Con.