A gun's sole purpose is for killing (guns weren't invented for sport shooting, before someone brings that up), or the threat of killing.
A bike has utility in that it can get you places. Apple products serve whatever their intended purpose.
Knives are similar to guns in that they can be very dangerous but they also have utility, such as in the kitchen or workshop. Few things can kill someone as quickly as a gun can, and they simply have no utility beyond their intended purpose. I can't use a gun to make a sandwich for example.
If I may offer you some some change of perspective
1) You've separated the utility of those other items from the by-effects of their utility. A bike gets you places...and the by-effect is that it emits harmful pollution and exposes the operator to the chance of death. Why not do the same for a gun? The utility of a gun is that it can stop multiple targets, at a distance, quickly, reliably and with no great physical strength from the operator and no compliance needed from the target. That is the intended purpose of every handgun on the civilian market. That's the utility for which consumers buy them. The by-effect of such a utility is that the target
can be killed. Invent
any tool that fills this mandate and it, too, will be lethal. That's simply the way humans and physics work. Which brings me on to my next point...
2) Consider this - you've attached a stigma to the utility of a gun, because its rather good at killing. Why? The free world is built on the shoulders of people who killed when the time called for it. Sure, we can try to hide that fact away in our airconditioned offices and glass-walled skyscrapers and online shopping and boardroom meetings, but imagine a world where killing was impossible. Whichever group of people was physically strongest and had the most numbers would be invincible and rule over everyone else! Killing is by no means a black and white, universally good or bad thing. You may disagree with this, but...
3) If killing is simply a one-dimensional thing that is never good and never right and must be stigmatized, then the
outcome of killing is all that matters, yes? In which case, why assign any importance to the tool with which it's achieved? After all, we aren't looking at intent and principle, or the context in which it happened. Killing is killing. Dead is dead. All that matters is whether or not an object is actually used for killing in the real-world. Of the hundreds of millions of rounds fired every year around the world by civilians, almost all hit a piece of paper or steel. The percentage of innocent humans harmed/killed is so tiny that you'd have to move over several decimal places to avoid rounding to zero. If we're concerned about outcomes, then the outcome of gun usage in the real world barely ever involves killing.
The reason I typed all of this is because I noticed you mentioned you're looking at getting a gun. The "intended purpose" argument is a form of emotional blackmail that the anti-gun lobby has been punting for years -
if you are in favour of gun ownership, then you must be a bad person because killing is bad. If you're going to get armed, it's important to understand the true purpose of the tool you're buying and the reason you're pointing it at a threat. Not to "kill". But to stop the threat to protect yourself. The threat might be killed in the process, which is not the same thing as you setting out with the sole purpose of killing them. It's important to come to terms with this before becoming a gun owner, because you really don't want to be contemplating all of this when it's time to actually draw on an attacker.