Has anyone used a Psychic Familiar in your games, if so what was it?

My Astropath has a tiny, psy-bonded Void Rhino we rolled up from Koronus Bestiary that provides him the ability to sustain an extra power and gain an extra Psy Rating on Telepathy. It's kept inside his armour, and is mostly just ignored (though will be killed if he ever suffers an explosive critical). It hasn't actively participated in fights, so it's been a nice boost for him.

However since the creature is unkillable by normal means according to Rogue Trader, the ship is now overrun with them like a plague of extremely ferocious mice.

Lol, I am actually more after story potential, although a bit of enhancement for my Astropath wouldn't be sniffed at

LOVE the 'plague' idea! Mind you, where did your Familiar find a 'friend'??

However since the creature is unkillable by normal means according to Rogue Trader, the ship is now overrun with them like a plague of extremely ferocious mice.

They're tribbles?

I'm not intending for my familiar to become involved in combat either, as it's not my intention for my Astropath to be too involved in combat (although, when he hits with his 'stick', what he hits usually stays hits ). Something that gives a slight boost to his usefulness for the party and mostly something to allow a little bit of role playing tomfoolery

Tiny void rhinos?

Nice!

I've played a Weirdboy with a Squig as a Familiar before. I was unimpressed with the stats they came up with for the WeirdSquig (which actually had an error) so the GM just let me take the base squig stats and roll up a new varient with Psychic Familiar tables.

I ended up with a Necrophage squig (+10 to toughness and regeneration provided it eats enough raw flesh) that was a coward and prone to wandering (but had an extended range of usefulness)

This made for a fun familiar that is tough enough (squigs get unnatural toughness) to wander around unsupervised but not aggressive enough to get into too much trouble.

Mostly it hides in the galley and wolfs down as much food as it can before it is discovered.