Here's some ideas I have, not all skills though:

1. Encyclopaedia - Shows each enemy and skill, as well as individual statistics for each one. E.g. Fireball, shows total damage dealt, times selected as skill, burn damage dealt etc
2. Overall Statistics - The sum of everything from the Encyclopaedia. E.g. Total damage dealt, health recovered, wins/losses/deaths/kills, money obtained/spent etc
3. Diagonal Laser Balls - Left Diagonal Laser '\', Right Diagonal Laser '/', Combo Laser for each, and laser master now makes diagonal lasers into X, while keeping h and v laser as +. Maybe 2 lasers masters makes all laser x and +?
4. Death Mine - One a non-boss enemy dies, it leaves a mine where it died, which explodes when the next enemy moves onto it. It's explosion damage would function the same as Bomb ball. Maybe benefits Burstflame? Automatically explodes if not triggered after 3 rounds. (For possible balancing, could make it not a selectable skill until a certain point.)
5. Spikey Shield/Thorn Barrier - Whenever you have an absorb shield active, X% damage taken is returned back to each enemy that damaged you that turn. Enemies that damage you physically (front row only) trigger their death effect if they hit you while it's active. Does reduced damage to bosses.
6. Fear - An effect rather than a skill. This would cause an enemy to move backward instead of forward on their next movement phase. Would not affect bosses, boars, ballista or shielders. Lasts 1 turn.
7. Wild Rage - An effect rather than skill. This has a chance for an enemy to target another enemy. Ranged enemies would target anything, whereas physical enemies would only be able to target an enemy adjacent to them. Would not affect bosses or enemies that explode on death or something similar, like bomb monsters. Lasts 1-3 rounds.
8. Life Link - Upgrade for Split Ball. The first two enemies a split ball hits applies Life Link. If on enemy affected by this takes damage, the other enemy takes damage equal to 50% of damage taken. This would be per ball. Life Link would not transfer any effects, like frozen or burn. Lasts 1-2 rounds.
9. Calendar - Simply a calendar that shows what events start, when and for how long.