This post is all about how to use the Executioner effectively. I realize this post may seem a bit early, but I decided to open the subject as there are a few key points I think everyone should be aware of before misusing this monster machine.
The first point I'd like to make pertains to the Prime and B variants. If you pick up this variant, the first thing you're gonna want to do before using it is change the weaponry. The firepower mounted on it is intended for long-range combat but is fairly sub-standard when considering it's a 95-ton assault. The idea behind this chassis is that it has the speed to fall back and keep engagements at long range. While this may be effective to some degree, a majority of maps really cater to brawler assaults, leaving long-range sniping to lighter mechs. You may want to swap out omni-pods entirely on this guy, imo the EXE-A has the best omni-pods (minus EXE-D which likely won't have available omni-pods for a while).
The second point I'd like to make is specifically towards CW. If you do decide to make your Executioner a long-range sniper, don't bother playing it in CW as you will be sorely disappointed. Most attacking strategies involve speed and/or brawling, where defense strategies involve heavy loadouts for multiple ranges. With the inclusion of MASC and a fast engine, there's not much reason to delegate your Executioner to a stand-and-snipe position, as other lighter mechs can yield the same amount of firepower and do the job better. The attack strategy of fast brawler, however, is what it excels at. It's got the speed to close range quickly, and it's got the hard points to mount a dizzying array of pulse lasers. It's even got the jj's to jump the gate and potentially mount an all-assault sneak attack. (fyi, you can expect some 12-mans to run all-EXE/MLX meta-builds, so they really could bypass the gates entirely if they wanted.)
Lastly, if you haven't opted to buy a package but you're still planning to buy some A La Carte or wait for C-Bills purchase, you may be wondering, "Which one should I purchase first?" If you're looking to only spend C-Bills, I suggest getting the EXE-A first. It comes with a decent amount of hard points that you can modify for some truly scary laser boating. If you're willing to spend some cash to receive the mech earlier, then I highly suggest the EXE-D once it becomes available in the Gift Shop. A little omni-pod swapping on this variant gives you up to 13 energy hardpoints! But be careful not to run too hot.
I'd love to hear more of other people's ideas on the EXE in this thread, maybe some loadout ideas. Have at it!