If you had a lvl 80 boost to waste...
If I didn’t have a necromancer I would get one of those, why? Because I main a Reaper. I have tried almost every class, and gotten every one except Guardian, and Reaper is just very versatile. Reapers are durable, they are not overly simplistic and there is a lot to mastering them, but you can play them without knowing all there is to know about them. In other words, you will survive even though you are learning how to use your Reaper. They do a decent amount of damage. Minions are a blast (actually, bone minions literally blast..lol)
I already had at least one 80 of every profession before I got that boost. But I didn’t want to use it on an 80 for the rewards, I did want to get the level up part too. It sat in my slot for weeks until I decided I really needed the shared slot. So I made a second Revenant, primarily because I’d had a few race/gender designs for my first Rev and had been very torn on which to make. Since my “real” Rev is a male charr, and since both my previous norn are medium armor types (plus I added a Light one to have a Reaper to match my beta alt), I made a female norn revenant in order to have an excuse to get T3 heavy norn cultural at last.
But I haven’t unlocked Herald on her, explored the world, or spent any resources beyond some transmute charges. She’s parked at the flax farm. After all, she exists just to give me another shared slot and to be a race/profession I’m not already swimming in multiples of.
I’ll join with Ophidia in telling you that Reaper is hands-down the most fun elite, the most viscerally satisfying rough-tough mob killer you’ll find (at least in my opinion; everyone has their fave). I have 4 Reapers now, though one of them is the one I actually use for Reaping. Only one Scrapper, Druid, and Daredevil, only 2 each of the heavy professions, two Tempests, and a lot of Chronomancers. Reaper is my go to for anything but fractals, as I have a chronomancer geared up for those.
If I had had an extra + didn’t already have multiple 80’s of every class… I’d prolly make a class I would use for both WvW & PvE… I find it easier to switch from character to character instead of moving gear around to change my build to suit my character… That way I can simply swap from Necro #1 for fractals to Necro #2 for WvW… Same with my Rev #1 & #2 and a few other classes…
Now if your asking which class you should get to 80 next & you don’t have every profession to 80 already that completely different… You could always go necro because they are viable in all game modes… You would likely need to get a set of zerker for genearal PvE and WvW but, a set of condi would be optimal for fractals & raids.
I used my boost on Rev to open up the shared inventory slot. I do have every other class level 80, sometimes multiple, so there really wasn’t any competition.
I’ll be the 4th how-ever to tell you, try Necromancer. They’re good at everything at the moment, raids, fractals, but also simply open world content with an extra HP-bar, good tagging potential and decent burst. (Assuming a power build here, which is not high-end meta but likely what you’ll run until you can make a Viper’s set if you’re just dying to go Conditions.) They can even step into WvW/sPvP and you’ll never feel weak.
Elementalist is a similar story to Necromancer if you really don’t feel like Necromancer. Good at everything, how-ever you’ll either be very squishy or give up quite a bit of damage not to be, this may or may not be your playstyle. (I love it :p)
Warrior / Revenant are also just solid to have, good self-buffing capabilities for anything solo and enough armor/hp to walk through content without too much of a worry. I don’t enjoy them too much but if I feel the need to do Living Story twice (for rewards generally) they’re often picked above my more beloved classes for sheer efficiency.
I’d avoid double classes until you had a taste of all of them personally. I never thought I’d like Engineer, but I ended up loving them to bits almost instantly after creation, same with Ranger.
Lastly, don’t worry too much about ‘wasting’ it. I don’t know how old your toons/account is, but you get bombarded with leveling scrolls (birthday present for characters) and tomes of knowledge (log-in rewards) for another level 80 by the time you’re bored of whatever you picked.