Bringing back a lot of the D:OS1 skills comes to mind.
Any in particular you had in mind?
Currently I'm trying to make a reckless assault skill. A skill similar to All in that damages yourself some in trade for higher damage. I'm using a system similar to Last Rites but the damage to the user is still through the roof even though I modified it.
Well, in a fully AI controlled fight between a lvl 10 Guard and 3 lvl 8 Flesh golems, The AI did not use the 4 AP fiery whirlwind, and instead chose to use regular whirlwind + ignition. I guess the AI realized I undertuned the damage.
It DID however use my Reckless assault skill when it was near death to finish off a Golem and died in the process.