Above, M-rated games are shown at Game Nut, 844 Mass. Store owner Gene Nutt says his store always has someone knowledgeable working who can answer concerned parents’ questions.

Brandon Siler, left, and Brenan Conroy browse through video games at Game Nut, 844 Mass.

Brandon Siler, 16, Lawrence High School sophomore: “I’ve held debates with my mother for days on end. Surprisingly enough, I’m usually able to win. She know what I can handle because when I was growing up she didn’t plop me in front of a couch and tell me to entertain myself.”

Brenan Conroy, 13, Central Junior High School eighth-grader: “If you can tell it’s not real, it should be fine. My mom still is restrictive when it comes to rated M.”

Sex. Drugs. F-bombs. Terrorism and sadistic murder. It’s not the stuff of most parents’ holiday gift lists. But if your kids are asking for video games this season, you’ll need to do a little research to make sure you aren’t inadvertently giving them those very things.

It’s easy enough to avoid obvious ones like the “Grand Theft Auto” series, which has received much media attention for graphic sexual content and rewarding criminal activity. But less-publicized games can sometimes have more subtle content that parents may find equally objectionable, such as:

• Gambling, real or simulated,

• Crude or “bathroom” humor,

• Sexual innuendo or other “adult” humor,

• Use of or references to alcohol, tobacco or drugs,

• Explicit lyrics in soundtrack.

There are 30 such categories of content on which every video game sold in the U.S. is rated. Based on each category, the games are given a letter rating — such as “E” for everyone, “T” for teen or “M” for mature — which appears on the front of the game. Turn the box over, and the rating is briefly explained based on the 30 categories.

For example, a title sure to be on many wish lists is “Call of Duty: Modern Warfare 2.” The game is rated “M,” and on the back of the box you’ll see “Blood, Drug Reference, Intense Violence, Language.”

Many parents may want to dig deeper though, and for that, it’s best to pare down your kids’ wishlists by looking up titles online before heading to the store. The rating agency’s Web site is the best place to start: esrb.org.

When looking up “Call of Duty,” you’ll get much more detail why “blood” and “intense violence” were flagged:

“The most intense depiction of violence occurs during a ‘No Russian’ mission where players take on the role of an undercover Ranger. Several civilians are gunned down at an airport as players are given a choice to participate in the killings (e.g., players can shoot a wounded civilian that is crawling on the ground), or walk by and observe without opening fire. In either case, civilians scream and emit pools of blood as they are shot to death.”

Another site, whattheyplay.com, calls itself “The Family Guide to Video Games” and typically goes into even more detail on why games get the rating they do. The site also offers a holiday gift guide broken down into “Kids,” “Tweens” and similar family categories.

Whether or not you’re up for doing online research before shopping, talking to someone knowledgeable about video games can be a good idea. It might help you make the hard choice of whether to buy your kids a borderline game that they really want.

Gene Nutt, owner of Game Nut, 844 Mass., says his store always has someone knowledgeable working who can answer concerned parents’ questions.

“My advice is to find a store that has a staff who will actually talk to you about the games,” Nutt says. “People in the industry have a really good idea — if you tell them what you’re OK with or not OK with, they can point you in the right direction. Some stores are much better about that than others. I think if you shop locally, you’re going to find that there are people there who will give you much better customer service.”

Ultimately the best resource may be your kids themselves. Game Nut shopper Brandon Siler, 16, says his mom, Holly, lets him bring home whatever games he picks out. It’s up to him, though, to convince her that a game’s suitable once he starts playing.

“It’s a constant battle around here,” Holly says. She doesn’t like games where the player commits violence against other humans, especially when there’s realistic blood. The last game she vetoed — “Manhunt 2” — was little more than just that.

“I watched him play it for a little while, and I was like, ‘No! No! That is NOT good!’ He fought me at first because he wanted to try it out, but I kept pointing out what I thought was wrong with the game and he quickly agreed.”

She says she will allow some violent games, but she doesn’t allow any drug references or sexuality.

“He’s always pointing out how ridiculous that is. And I agree. But I just don’t want it to have drug use, or naked women or men,” she says.

But even that restriction isn’t always black-and-white. Remember “Grand Theft Auto”? She’s OK with that game, Brandon says, because he doesn’t explore the sexually explicit and drug-riddled parts of the game that got all the media attention.

“I’ve never really gone for the stuff that they put in there for shock value. She understands that, so she’s more lenient,” he says.

“Ratings aren’t always accurate. If that’s the case, or if she’s reading into something that’s not there, I’ll debate the point,” he says. “But she’s got the final word.”