Background.The Knight Paladin is something of a baseline entry unit in many ways. This is because in the background it is noted as the most widely employed type of armour and the array of weapons it can potentially take.
Like other knights, it can take a household rank and has an ion shield for an invulnerable saving throw.
The ocular augmetics upgrade give a situational night vision rule, but more importantly can give a re-roll of a 1 on the vehicle damage table. This is therefore a type of knight that should have enemy armour in its sights.
The basic weapon is Ordnance 3 at S=6, but this can be upgraded for free to a more common (at least in 40k) rapid fire battle cannon for two large blasts at S=8 instead. This is probably worth it to be honest. Equally, if you're facing lots of on-foot infantry (Raven Guard perhaps?), then the original battle cannon is probably superior. I would still contend that the rapid-fire cannon is a bit more generalist due to the higher strength.
Between the reaper chainsword and some stomping, the Paladin Knight is a great close combat exponent that enemies have to take seriously.
Naturally, there is a bit of a drawback to the ocular upgrade benefits, which only kick in at a range of smaller than 12 inches. Therefore the knight has to get close and fast to any enemy tanks to take advantage of the bonus associated with this.
The bio-corrosive rounds for the heavy stabbers are a bit odd to my eye in some ways. They're supposed to be a bit more of a threat to things like monsters on paper. But that's situational obviously. Just take the reaper chainsword to them instead probably.
There's probably a couple of builds in there, but I think the following one is the baseline, and probably the best as well.
Questoris Knight Paladin, Rapidfire battlecannon (375 points)
Team up with almost any household rank, and its good to go.