Well I figured I'd list the builds I've been using (built from memory, so their may be differences):
LB20X Scorch Devastating up close. It's rare I don't outright kill at least a couple mechs with this. I don't run Artemis, since I've long since learned to deal with spread (which was reduced recently anyways).
Sniper MAD-IIC-D ERLLs very close to the cockpit and dual gauss for long range fire. A Pair of SSRM6s keep pesky lights from deciding to stay to long anywhere near you (especially will you can go into counter ECM if they have their own ECM).
MAD-IIC-C The Dual UAC10s are the main firepower, you can ride them while generating very little heat. When you need to bring more firepower tap the MLs and make them feel some pain.
Vulcan MAD-IIC-A Few people want to stand in front of the stream of UAC shells this can fire. It uses MPLs compared to the C's MLs to make up for the difference in number.
MAD-IIC-8 This build is to hound the enemy. The ER PPC and LRM can work at long ranges, but the LRM is best used to hit enemies who duck behind cover before you lose lock. Replace the ER PPC with a LPL for better heat management for similar damage. I split the ERMLs into threes (arms and torsos). This mech can still do fairly well having lost a leg, a side torso and both arms (I've had it down to 12% still fighting and lived).
Superhot MAD-IIC The ER PPC is only there to provide a bit more range in long range engagements. Otherwise it's all the MLs and LPLs, If I could get away with 3 LPLs fired together I'd use that instead of the PPC.