Honestly for me there are only 3 weapons on Crisis. Plasma Rifle, Fusion Blaster and Cyclic Ion Blaster.
CIBs are just awesome. They can threaten pretty much everything (although not the most efficient weapon against high AV an 2+ armor obviously) which means if you want a slightly more multipurpose approach you can pair a CIB with either Plasma or Fusion Blaster.
If you have spare points make the PR or FB twin linked if you want to rely a bit less on Markerlights with them.
Due high firerate and high strength they are still decent against everything you'd want to shoot at with your Plasma Rifle or Fusion Blaster as long as it's not AV13-14.
Why no Missile Pods or Burst Cannons? Well for long range S7 dakka we have Broadsides or Riptides who do that job much better unless you fight on a dense terrain board with no proper line of sight for the Broadsides. And Burst Cannons are pretty lack luster. 18" S5 AP5 is REALLY nothing we are in dire need for as Tau and CIB with its +2 strength +1 AP easily outclasses the -1 shot.
The wild card would be the Flamer I guess. It's incredibly cheap, offers nice Supporting Fire Overwatch capabilities and is a pain in the ass for a lot of armies if you drop 2-3 Monat units with double flamer in their lines just because you can...one costs only 32p anyway.
Also one shouldn't underestimate the amount of damage they can do. Sure S4 AP5 is worse than the Burst Cannon and they have less range but they also don't need to roll to hit and ignore Cover. If you are in range you should easily get 4 hits per flamer on a unit off while a Burst Cannon would do only 2 hits on average without Markerlight support.
The Airburst Fragmentation Projector is......as bad as its namechoice. I mean it's not bad bad but it's definitely not worth 15p. A 5" blast with barrage? Sounds awesome! S4 AP5 ignores cover? Flamer profile, okay still good! 18"? ....what?! Make it 30" and I'd say it might be a good artillery platform for 15p considering Crisis can do their JSJ shenanigans.
Overall the most important thing got already said. Don't look at your Crisis and think about a good loadout for them. Look at your list and think what you are lacking and fill that void with Crisis.