Some reasons : Gunslingers are so awesome (Tank vanguards too)
Gunslingers are just so awesome. They're my personal favorite class and they're the only class along with guardians who have balanced specs (Marksman being all about burst damage - My personal favorite, Saboteur being AoE damage over time and defense and Dirty fighting being a pure damage over time spec). I know there are a bunch of people who didn't like this game but honestly, I like the game and it's one of my favorite games to play as of now. Here are the reasons why gunslingers are so awesome.
1) Awesome animations and great costumes (The looks)
The class has simply awesome and cowboy-esque animations. From aimed shot, to quickdraw and all that. All 3 specs give the cowboy-style and smuggler like feeling. Well, maybe not saboteur because I don't remember smugglers being fond of throwing charges and grenades at their enemies. Oh and, their costumes are simply awesome. You can be a space cowboy! How cool is that!? Maybe not for some but for me, damn that's just awesome.
2) Dual wielding
Two pistols are better than one right? This applies for the gunslinger. Although, having non-matching dual pistols tend to look weird and awkward, it's still cool to have two pistols. That's not to say that sniper rifles are lame and all that. In fact, there are some slick looking sniper rifles.
3) Playstyle, specializations and dat DPS
Their damage is insanely amazing. Holy crap, I thought that being a one-dimensional dps class would be lame but then I was wrong. IT'S SO FUN. HOLY CRAP. The specs of this class is amazing! Well balanced and not over powered even though if there are some players there raging about it. Really, they're not overpowered.
4) In PvP, this class is the dark-horse/hidden god class and is also usually ignored (Low priority target)
Well, I wouldn't say God class but this class is awesome in PvP. Whenever you dive into the fray, no one attacks you (Most of the time) which means you get to burn them down while they take out the tanks and the healers. That's the perk of being a one-dimensional dps and the disadvantage of being a healer. As a healer, you're a walking target that has to stay mobile. As a dps, you just kill people and stuff. Really, that's all what you do against most classes. Don't take being ignored as an insult, it's more of an advantage.
