A bunch of those already exist.
If you have KM, take a look into scripts/custom/Techs and scripts/ftb/tech.
A Poleron beam, i.e. a beamweapon that phases through shields does not exist yet.
Probably because it might be too tricky to implement properly. AFAIK you can't prevent shields from stopping beams. The phasing torpedoes circumvent this by creating a second torpedo at the impact point of the first and giving that clone the originals velocity.
For a beam weapon you'd probably need to create an (invisible) small ship (probe or similar), give that the original ships beam weapon (adjusted for damage drop of due to distance!), constantly reposition that ship along the shields, to the point of impact of the original beam. And then get that ship to shoot its weapon at the correct targetsubsystem for as long as the original weapon fires.
The hardest part here is probably the positioning just inside the shield buble. And there were some unforeseen consequences to attaching invisible ships to objects from what I remember.