1st scene ultimate weapon. ANY other mêlée weapon in the game just gave a different animation. The only great thing in AC4 was the ship upgrades, because they genuinely made the game easier. Ranged weapons as well, but only to the point that ranged stealth-kills were possible. Many other AC upgrades were pretty much irrelevant until part 4.
I don't really blame the game for that. A decent combat system that the AI could use as well (or a proper stealth system) would have made the game unplayable. It's a story, and not too bad of one. Blaming useable (and easy to use) mechanics for what is an action-adventure romp is like blaming Star Wars for being a little bit crap cinematographically or having a poor script (or actors). It's a fairly good action-adventure regardless.
But anyway, Watch Dogs. Looks good. Don't expect too much. Not very much "blows our mind" anymore. Should be a nice little action-adventure-intrigue romp with a good story and some alright mechanics though. Looking forward to it.
edit: (actually, now I think about it, ranged weapons that were stealthy in AC4 probably went too far. It wasn't exactly a limited supply, so when you wanted to, the stealth/combat/or health system became irrelevant. But linked to an overly easy stealth system it didn't matter too much in gameplay terms regardless. Still, it mattered as an upgrade. Better than an inconsequential cash-earning villa in any case).