The first I always have to think of is Savagery as a Warrior card.
It wouldn't be amazing, but alongside bigger weapons like Gorehowl and Arcanite Reaper, you effectively get another 2, albeit somewhat limited, Shield Slams. Not too shabby.
To this day, I don't understand why Druid has this piece of trash anyway. I know it was pretty good in Beta, when it was still an AoE effect, but that was also before Bite and Claw were changed/nerfed. Ever since, this whole Hero-Attack theme in Druid is clunky, underpowered, and pretty much worthless outside of the two infamous wild Blood Magic Tavern Brawls... where Savagery wasn't used either.
Alternatively, I think adding Light's Justice to Druid could also be an idea. The Druid Hero Power is pretty much the worst in the entire game, has no synergy cards outside of Savagery and Savage Striker, doesn't support the class for its primary playstyles (or what's left of them), and I think adding cheap, weak weapons would be a natural fit. And Paladin has not much use for it outside of getting it for free in Muster for Battle.
There are certainly many other examples, but these are some of the first that come to my mind.