Time for the classic Necron unit, the Monolith. Frankly this is one of the models I think they've pretty much got right. Lets go into what changes I would make.
Bs: 4 F:14 S:14 R:14
Tank, Skimmer, Transport capacity 20 (Immortals count as 2 models, Tombspyders count as 3)
- Particle Whip: Str 4 Ap4 24" Heavy 1, Large blast, ordnance.
- 4 twin-linked Heavy Gauss Flayers
- May replace power matrix with four Particle Projectors (see tomb spyder entry), their shots may be combined to fire with the following profile: Str 10 Ap1 72" Heavy 2, Twin-linked, Melta
- May replace all twin-linked heavy Gauss flayers (see immortal entry) with a defensive discharge system: (deals one S4 wound to each unit within 12" of the monolith for each model in the unit within the 12" area of effect.)
- Power Matrix: once per turn you may choose one of the following options:
- Fire a particle whip with the following profile Str:9 Ap3 36" Heavy 1, Large blast, ordnance
- Charge the Defensive discharge system: deals one S6 wound to each unit within 18" of the monolith for each model in the unit within the 18" area of effect.
- Charge the portal: models embarked in a vehicle with a portal may disembark anywhere within 12" of the monolith, any number of units may disembark this way.
- Living Metal: as in current Necron codex
- Ponderous: The monolith may only ever move up to 6" in any movement phase. It is always treated as having not moved. Furthermore, ponderous vehicles may fire ordnance weapons in addition to their other weapons.
- Portal: Models embarked in a vehicle with a portal may disembark from any vehicle with a portal on the table. Each portal may only be disembarked from once each turn unless otherwise stated. Models may embark into a vehicle with a portal as long as they are within 6" of it instead of the usual 2". Furthermore units may disembark up to 6" away from a model with a portal. (keep in mind that a unit may not embark and disembark in the same turn)
So looking back maybe I did make a few more changes than I thought I had. I added some weapon options to create some variety and make it so your monolith will work how you want. I also decreased both the particle whip and defensive discharge array to str 4 so they count as defensive weapons, this is so no matter what other weapons you are charging with the power matrix you may fire both the defensive weapon and the ordnance weapon.