I have a katana with hit lower attack, hit lightning and swing speed increase and FC1 that serves me very well. The other, useless, mod is troll slayer.
I have a bokuto with HLD and HLA and HCI which is also very good. I prefer the katana.
I have an executioner's axe with SSI, hit fireball and HCI which is good until I start running out of stamina, which happens every fight (I use it mostly for bleeds).
I have a hatchet with hit lightning, stamina leech, hit lower defense and damage increase (have to include that since it isn't a crafted item) which is VERY effective indeed.
But it's different for each weapon. An ornate axe without SSI, for example, is pretty much useless. But a kryss with SSI has a wasted mod unless someone's stats require it (i.e. low dex).