Guy is a general term most times, but I've known a few women that get offended by it because they aren't male.
Dude is also used for both, but a lot of folks don't want to use that in the office. Alternatively, just use person and be safe.
Hey I'm offended you used the word op. When I was a kid, these kids used to bully me by calling me an Op. Can you refrain was using that word.
This is very much a cultural issue. From my time in Korea, a young person speaking to an older person in a familiar way would've been a major faux pas. On the other hand, the reverse (and consequent potential for put downs on the younger person) seemed quite common (older referring to younger more familiarly than had been earned). Similar experience in Spanish-language communities and cultures. English, particularly American, speaking communities have developed an incredibly tendency towards informality and unearned familiarity in our language. That's not a bad thing, strictly speaking, but it is something to consider.
When you enter into a professional setting, or a setting with people you aren't familiar with, just speak to them in more formal, professional, or polite ways and you are incredibly unlikely to offend someone (outside the occasional, "My father was Mr. Such-and-such, I'm just Bob", or random enlisted Army guy, "Don't call me sir, I work for a living"). It is stress-free if this sort of language is something you practice on a daily basis, it's just how you speak to people.
Yeah, horrible choice of words on my behalf :)
There are a few people who get upset over it or intentionally make a vocial issue out of something that isn't. ("Guys" is generally a genderless term ["You guys, take a look at this!"]
Yep. It's the northeastern influence on my mannerisms.
However, I would not say that some people get offended by everything or that they are looking for things to get offended by - not in a professional environment at least. Though I believe it to be reality, I think saying this bit would cause more problems than the word, "guys".
I'd also avoid the term, "guys and gals", but that's mostly because I dislike it, but that's just personal preference.
And it crept into my English vocabulary. I think I sound weird when I use it sometimes, but you are the first to point it out :)