I don't play anymore, but when I did I specialized in hiding in out of sight before something got captured and then portaling up people to recap it. It was so much fun. I came up with great hiding places myself that people never really checked. This was on a tier 1 server so a lot of big scale action going on at most times.
I also liked roaming with mostly zerker gear and trolling groups with stealth and blink bursting down single targets and then running away. I also liked trolling everybody on my tanky ele, but I liked my zerker gear mesmer burst more. I just felt so powerful on my mesmer being so slippery, bursty but fragile at the same time. I dropped like a potato once people focused me but I had no trouble running through a crowd of 50 people sieging the gates of our objective with stealth and immunity shatter/dodge. Pulling people from walls was also fun.
I also liked dominating the arena in the jumping puzzle, portaling people up from my server while stopping the other server from getting past the arena. Kinda mean, but so much fun.
WvW is imo one of the best features of GW2, worth buying the game for.
Don't get me wrong the game is far from amazing, but WvW was the highlight for me.
Mostly Mesmer with some Guardian. I did level my Necro in WvWvW a bit, but I don't think I'll keep bringing her in.
I often run Mes duty. So veils, portals, hiding in keeps, etc. When not with the big group, I solo what I can. That includes yaks, sentries, guards and camps. If guildmates are on to do guild activity, I'll run havok group. If there's nobody on to command, then I'll tag up and lead the militia. If the regular commanders are drunk, then I tag up and lead their guild. If we really lack scouting and I'm semi-busy with other stuff then I'll scout or sit in a keep to watch it.