>Q. Why would you ever suggest Sunkern for anything Pokemon-related?
Sunkern, despite it's devastating stats that give him/her the title of lowest base stat total, is in fact a beast at the Pokeathlon. Each Pokeathlon stat has a potential of 5 stars, but you will need to train it up for the Pokeathlon. Once you get it to reasonably high stats, slam it in the Pokeathlon and it will smash! :'D
Unless you wanna look on this list for yourself, I don't think any other Pokemon has potential like this. So, I'd highly recommend Sunkern. Just for the sake of finally using Sunkern in anything. xD
Also, for a strategy for the Pennant Capture, I hate that game as well. I tend to go get the flags when all the other Pokemon are off the screen. So, good luck!
Hope I helped. :)