There's really a wide variety of stuff you can get to work, but here's a bit of info on some broad types.
CI Caster using Freezing Pulse or EK (or switching between the 2). This type of build generally will look something like
this, dropping the elemental/cold stuff if you're EK (EK is better vs all the Aegis Aurora blockers so its likely the superior option). This build isn't really much in favor right now. You can also do a Pain Attunement version if you have a Shavs.
With melee, you can either do swords or daggers, and do either CI or HP. Daggers are more DPS in general, but swords have passives which allow you to bypass enemy block to some extent, and since block is so prevalent in PvP this is extremely valuable. CI makes you immune to Viper Strike which is very nice, plus if you can disengage combat long enough you can regen your ES. However you're very easy to chill, and since you can't Blood Magic your skills managing mana can be very tricky. HP lets you regen life all the time, do Blood Magic skills, and be resistant to stunning and status effects.
Rough CI dagger build.
Rough HP swords
Again you notice the investment in block. Any shadow build will want a lot of block, and having a Saffels Frame and/or Rathpith Globe to swap into will also let you block spells.
The good points about melee shadow are fairly high DPS, high mobility and chasing ability with Whirl/Leap and flicker, and decent survival. Your main attack will be Double Strike, with Puncture and/or Viper as an alternate attack. Doublestrike will have all the usual melee damage supports, and I highly recommend including multistrike whatever you do, as the autotargeting is very useful sometimes.
There's a huge amount of room to play around with here, but hopefully that's a start.
