Top 3 Secondary Weapons
Proper Disclaimer. Some of the weapons or frames are hard to get.This is pure opinion and can proceed through the story line without this.
1. Catchmoon Kitgun
While we are on the subject of mini versions of primary weapons, we should discuss the Catchmoon Kitgun. You can build this at Fortuna if you have enough standing, and the right components. This weapon will blaze a trail through any mission you are playing, and is the perfect weapon to accompany a Sniper Rifle primary, just because it does so much damage to so many enemies. I'm a fan of the Catchmoon + Splat + Haymaker build. Be warned though, it hits so hard it can tempting to not bother exploring other Kitguns, but you really should try out some other combinations.
2. Sicarus Prime
The Sicarus Prime packs high base damage that has a great balance between Slash, Impact, and Puncture. It also has a great Critical Chance and a decent critical multiplier. The burst fire nature of the weapon rewards accuracy, so people with great aim and recoil management will be able to get the most from this weapon. It should be noted; a Fire Rate mod will reduce the time between each round of the burst, making this weapon much more manageable. It is also worth noting that the high-Status Chance makes this weapon good for hybrid Crit/Status builds.
3. Lato Vandal
Not many people are going to put the Lato Vandal on their list of best Secondary weapons, but those people are wrong. Or I am. Someone is definitely wrong. I just love the Lato Vandal and always have. It sits in a nice middle ground between weapons that spam damage, and slow firing weapons that hit hard. It has solid base damage, high slash damage, and a high critical chance. It also reloads very quickly, meaning DPS downtime is limited. Finally, because not many people have it, and not many people use the standard Lato, you can get some pretty serious Rivens for this if you are lucky.