What Esca said:
the weapons lose a lot of durability very fast (I think 10 for every single time splintering weapon goes off). So people are looking for clean weapons only (unless you just want to have a short bit of fun).
For PvP it should be one handers of course, because of pots.
High in demand are weapons that have bleed as special move, because it stacks with the splintering effect and they should be fast as well. If you have a weapon with splintering that doesnt have bleed attack, you will probably switch weapons once splintering is in effect.
The thing with the cleaver:
it also has infecting as a special move, which means with the right temp you can use splintering/bleed and apply lethal poison with one weap.
Other very useful weapons with splintering would be war forks (bleed and disarm).
Paired with a hit spell they are even deadlier.
Gargoyles have an artie weap called: sword of shattered hopes with 20% splintering weapon & bleed/mortal which was (is?) used a lot. Also some glass staff with the effect. So the property was only available to gargs before shame changes, as far as I know at least.
Hephaistos of Europa