In my last game I fielded a potentially unusaul Psyker. Pretty much no upgrades, save a Spell Familiar, and replaced his Pistol with a Chainaxe.
Truth be told, I've never been one for using psykers to begin with, so it was nice to see my first ever use was a success (succesful Psychic test, followed by 3 out of 4 Smite hits wounded).
The main focus is the use of the Chainaxe, as it is technically effective against most races, due to being AP 4. This puts a lot less pressure on the use of the Force Weapon, meaning a Lvl 1 Psyker can easily be a threat at range (see previous Smite).
A thought occured to me also, that the Chaos Sorcerers' Force Weapon can technically be swapped out, for a Combi-weapon or Plasma Pistol. In my mind this allows the Player to utilise pretty much any power the psyker rolls, as projectile powers wouldn't be as high priority.
Do many others experiment with their psykers, or do most just use the base psyker with Mastery upgrades?