There is an achievement called "Minimalist", which is achievable when you: Complete the main story using only knives and handguns. (Excluding specific battles.).
This does not specifies which handguns and knives to use, however judging that Leon starts the story with his Handgun (SG-09R) and Knife (Combat Knife), is it the only weapons that is permitted to use? Or, is all handguns and knives are allowed to achieve the Minimalist?
Every handgun and knife is allowed to be used to achieve the Minimalist, so you do not have to limit yourself to just the starter weapons. If you are unsure of what exactly counts as a handgun, check which ammo type it requires. If it is handgun ammo, you're good to go - that is a pretty good tell if you're unsure.
Also, be careful of the Magnum - while many people think it is considered a handgun it is not and it will make you void the achievement.
Consider checking out the trueachievements website, it has a lot of good tips on most achievements including what will void the achievement and what will not, as well as recommendations for strategy.
As a more general answer, if you'd like to be sure if a gun or action falls under the umbrella of a challenge, you can check Current in the Challenges section, as in the screenshot below (I already finished the Minimalist challenge, so just switched to another "Don't Do X" mission). The number displayed is the number of times you've broken the condition of the challenge.
