Armajet Guide

This weird weapon is a radioactive goo launcher. The projectiles that it fires break into smaller globules on impact and stick to surfaces, dealing damage on contact.
Unlike other more direct damage dealers where you aim in the approximate direction of the enemy and pull the trigger, the Venom is a support weapon. Specifically, I like to refer to it as a *Zoning* weapon. I'm borrowing this term from fighting games and MOBAs but for those of you unfamiliar with the terminology I'm borrowing, this essentially refers to the ability to influence your opponent's movement. The Venom isn't necessarily about racking up your personal kill count - thought it most certainly can do this - it's about denying the opposing team access to certain paths, or entire areas of the arena.
Before we cover this more advanced level of use, let's go over the basics of the venom first, and how to use it outside of team environments.
Like the Badger, the Venom fires in an arc. It's also a burst-fire weapon that launches a handful of globules. As previously mentioned, these globules break apart when they impact into terrain, and they bounce. This means, like the Tremor, it's often better to aim, not directly at your opponent, but at the ground by their feet, or the wall or ceiling behind or above them.
In fact, these bounces travel surprisingly far, and with the curvature of the weapons trajectory, you can rain toxic goo into your opponent's whilst remaining out of their line of sight. A particularly cunning Venom user will also very quickly work out how to bounce these shots to hit targets in a frightening radius around them - for example, standing here near the Invisibility powerup on Magma, a venom user can hit opponents anywhere in this area - including directly below them. No other weapon in the game can do this, and this advanced knowledge of the maps is absolutely vital to vanquishing with the venom (roll credits).
Seriously though, learn the environments. Learn how your shots bounce from different surfaces at different angles. Get a feel for how this aspect of the venom works and you'll be able to rinse the opposition from relative safety.
Add to this that the Venom has a decent rate of fire, a fairly short reload time, and good mobility, and the Venom can very easily become very toxic to deal with, pun wholeheartedly intended. That said, however, dealing with a Venom user is surprisingly obvious when you stop and think about it.
Firstly, it's horizontal and positive vertical range is astonishingly short. If you approach a venom user side on, or from above (think 9 o clock to 3 o clock on a clock) it can be very difficult for them to deal with, especially if you keep to open spaces to deny the venom user a surface to bounce their goop off. You can easily swoop in and cut them to ribbons with a Blacktusk, Dominion, Thunderstorm... You name it. Any quick firing close range weapon will do.