Since there seems to be a lot of questioning about this particular ability, I'm going to delve into one of my personal favorites: Compoundeyes.  Remember, this ability adds 30% of the accuracy of the move in question, not an overall total.  So for example, at 70% accurate move becomes 91% accurate (70% plus 21%).  This means that moves with 77% accuracy or higher will be 100% accurate.  Below is a list of moves that CAP2 would be able to use much more viably with this ability that wouldn't normally be considered:
Supportive:  CAP2 would benefit from many of the moves it could know naturally getting a boost, which could make Sketch into an interesting option for sets that want to run Screens, Double Status, Trapper, and other concepts.
- Will-O-Wisp:  While it will most likely be considered for CAP2 regardless of ability, Compoundeyes makes CAP2 the best Will-O-Wisper in the game.  With a nearly perfect 97.5% accuracy rate, this thing is almost guaranteed to be passing out some burns.
- Leech Seed:  Although minor, it would have a 100% accuracy rate, which is kind of cool.  If you've ever used Ferrothorn, you know how it feels to have this miss.
- Stun Spore:  Like WoW, it gets boosted up to 97.5% accuracy, which is a pretty fun way to spread some paralysis.
- Magma Storm:  Although an offensive move, it would get boosted up to 97.5%, which makes CAP2 a niche trapper.
Offensive:  This is where Compoundeyes truly shines.  Many moves that wouldn't always be considered for CAP2 suddenly become viable through Compoundeyes.  Check it out:
- Blizzard / Thunder: These would reach a solid 91%, which gives CAP some really powerful coverage moves through Sketch.
- Fire Blast: One of the most debated coverage moves for CAP2 is Fire-type.  In this situation, Fire Blast hits 100% of the time, which is a thing of beauty.
- High Jump Kick: You may laugh, but HJK coming off of a Pokemon with 120 Atk AND fearsome coverage with complimentary Ghost-STAB is going to leave a mark.
- Megahorn: Perfect accuracy on the strongest Bug-type move?  Not necessarily the optimal choice, but at least the choice is there now.
- Overheat: It won't miss with this ability.  Plus, that coverage of a Fire-type move with 140 SpA is great.
- Focus Blast: The Special side of Fighting-type coverage rolls in at a reasonable 91%.  Focus Miss haters rejoice!
- Leaf Storm: 140 Base STAB that never misses is pretty nifty.
- Power Whip: Phew.  CAP2's notable Attack stat and STAB Grass-type make Power Whip a perfect candidate.  Step aside, Tangrowth, CAP2 can hit harder AND with impeccable accuracy.
- Stone Edge: IT WON'T MISS.  Even though it's not the optimal choice for out project, it is still much more plausible that it used to be.
- Seed Flare: At 100%, it's a pretty safe choice for CAP2 to rely on Sketch for.
- Circle Throw/Dragon Tail:  While not the BEST moves out there, their perfect accuracy could lead to some creative status shuffling sets.
- V-Create: 180 Base coming off of 120 Atk stat to provide coverage with a guaranteed hit.  Wowza.
I hope this list helps for your consideration of Compoundeyes!  As I think of more moves that are assisted by this ability, I will update the list.