You know, hunkering down and letting your enemies eliminate each other is actually a solid battle strategy. If your character is handy and depending on the type of battle royale they’re in/lay of the land, etc, then it’s possible that they could actually take a Home Alone approach which is make a castle and booby trap the crap out of everything.
The same problems would accompany this approach as a long siege, such as lack of provisions, boredom, and the fact they have no idea what’s going on around them.
It’s up to you to make it interesting though.
The short answer is that you can actually pick anything you want, a weapon’s use changes based on how you do or don’t use it. There are no “safe” weapons, they’re all dangerous. Your character could pick up a rifle and take it with her then only use it when defending the stairwell up to the area she’s chosen as her “safe space”. That’s using the weapon defensively, rather than kicking the door down into someone’s house and going in guns blazing. Going in guns blazing is offensive.
It really is all about how you choose to use it. Weapons don’t make you anything. They’re just tools like every single other tool out there. They’re made to do a job, but the one who wields them chooses the application.
Your character fights defensively or wants to, but there are a lot of ways to do that and how they do it is going to depend a lot on the rules of the Battle itself. How it’s set up, what they have access to, where they can go, etc. Defense is often defined by offense and vice versa.
The best way to defend yourself from combat is to avoid it, get away from it.
Get to higher ground, find a place where your character knows they can control the terrain, and prepare to defend it after the easy pickings have been picked off.
Try to remember this though: your character fights defensively and injures someone so they can escape, then that person will be picked off or killed by someone else later. Shuffling the blame doesn’t make them any less of a murderer. This is a natural course that some people do choose to take because they are trying to protect their morality or they can’t stomach killing. Your character can choose to do it, just recognize that this doesn’t actually make them a better person.
There aren’t any save your morals softballs in this situation unless your character’s end goals are a prison break. The hunted either eventually becomes the hunter, turn the tables, or they do something else to ensure they get out alive… or they don’t. They die.
Unless you’re changing the rules a lot, a battle royale is essentially a survival story. It doesn’t matter if it’s Ridley Scott’s Gladiator, The Running Man, or 2000′s Japanese action thriller Battle Royale. Your character’s goals will change how the narrative plays out, their desires and their wants. Revenge on the person or people who betrayed them/put them in this situation. Desire to survive, live, go home to their families. They need money. Whatever.
“I want to survive but I don’t want to kill anyone” is a classic cliche, and the point of this one narratively is that the character is eventually forced to choose. They must choose between their own survival and their desire to not kill anyone.
For example, The Hunger Games could have ended with Rue as the victor. The narrative links Rue to Katniss’ sister Prim as the innocent child. The role of the protector is to save the child and inevitably to sacrifice their life for them. This link would cause Katniss to sacrifice her life after everyone else died to ensure Rue’s victory. Natural tragic ending to the trope.
Every character has multiple paths based on the narrative themes you choose to play with and ultimately those themes are going to be more important than the weapons you choose to give them. They may have synergy with their weapon or not.
You can have them pick a weapon they have no idea how to use based on a very different decision making process. This can lead to a fascinating series of events all on its own as the character learns about violence on the go.
If your character doesn’t know much about weapons, then they’ll pick based on what they think the best choice is rather than what your or I do. I don’t pick weapons based on what I think the best are for the situation. I actually pick them based on what my character knows/understands about the world/their own training with a side of their personality. While one of my characters can use multitudes of weapons, she really, really loves her shotgun. You could not pay her to fence with a 19th century British saber, but she could kill you with it. Another of my characters loves her longsword because she practices HEMA. Another you will only ever pry her Glock 17 out of her cold, dead fingers.
They all have very different versions of what “defensive” looks like or would look like, even if you dropped them into a Battle Royale. The first one would avoid everyone they could and just make a beeline toward whoever dropped them into this situation, making the executive choice to only murder those responsible and the ones who choose to stand by them or get in her way. The second would try to get the participants to join up and work together in order to figure on a way out. The last one would win the competition and then kill everyone involved on their way out.
All of these options are actually defensive, even when taking the offensive. Defense is protecting yourself from harm. That’s all it means. Whether that’s a blocked punch or murdering the stalker following you through the bushes that’s planning to put your head on a spike. Fighting defensively can simply be not aggressively pursuing your enemy. Or aggressively pursuing the right one. In females A, B, and C above you see three different choices that express their personality types and their morals.
A doesn’t care about the Royale itself or the people in it, but she’s interested in ensuring it never happens again. Instead of accepting the status quo, she’ll go after the source. It will most likely end brutally and there will be spectacular explosions as an example is made.
B would like those smart enough and willing to survive actually manage to survive, she’s the type of leader who pulls people together making the most of their skills in order to figure out an escape plan.
C knows her best chance at killing those responsible is to play along, so she’ll play the game perfectly until the end when she murders them all.
Defense is what you make it.
So, what does your character think a “defensive” weapon is? A gun? A knife? A cudgel? A can of pepper spray? A tazer?
While it’s good to give your character a weapon that is appropriate to the situation, it’s doubly important to give them a weapon that they understand how to use. If you pulled up a list of weapons off the internet and stared at the pictures, what weapon would your character gravitate toward?
Research that one. Figure out it’s strengths, limitations, how it is normally used. Then step back to your setting, the events that will be happening/playing out in this battle and think about what you’ve learned about this weapon from your research. Whether they’ll work well or not doesn’t matter because that’s what your character picked.
Don’t munchkin it.
Roll with the punches.
Figuring out how your character will choose to use their weapon in the environment and circumstances they’ve found themselves in is half the fun.
Their weapon is not going to save them. They are going to save themselves. Maybe the weapon will help and maybe it won’t, maybe it’ll help them in some battles but not others.