Canoptek Wraiths: Wow, they did a great job with this unit despite some changes. They are now a jump unit with rending ignore difficult terrain and pass all dangerous terrain tests. So, you can deep strike into scenery without worry. Second, you can take some upgrades for them; the particle caster gives you a STR 6 pistol which is nice if you deep strike behind something with weak armor, granted the range is only 6”. The Transdimensional Beamer forces a STR check or they disappear from the table, this is nice against weaker races like Orks, Eldar, Dark Eldar and IG that can allow you to single out models in a unit such as champions, special weapons and heavy weapons. The Whip coils forces some models to go to Init 1 which can cause fits for a Grey Knight player that smirks knowing they are going to get to use their power weapons first. NOT! In theory you can even build this unit into a complex unit taking one of each upgrade to wound distribute.
Canoptek Scarabs: Oh, these guys will be the favorite! Fearless swarms that move as beasts and has Entropic Strike. These guys will draw much fire and leave a mech player cowering in cover. Swarm a few tanks and CHOMP!
Tomb Blades: A second wave model for the Necrons and simply they are jet bikes. IMO there is better options out there but they could still offer a nice chance of pace if you’re bored with the other Fast Attack Choices.
Necron Destroyers: Now your heavy destroyers and destroyers are one. You can build up a mixed unit and take all your earlier hits on whichever is the better deal. A few heavy gauss cannons are a great deal now that they are no longer fighting for a heavy choice. Also Preferred Enemy (everything) can be helpful against opponents in a pinch.