My favorite one is the Cross-Cultural Communications one. I can usually get 20 coins even if nobody else joins. The majority of the visitors are non-English for me. Except one guy which really pissed my off, he said "Bon Appetit" but then claimed to be playing in English. They shouldn't use loan words for this kind of thing. I usually cycle around between Type matchups, CCC and Break Boulders Quickly.
And speaking of the PGL, I've taken a look at the Friendly Competitions and it's pretty disappointing. The selection criteria seem to be lacking a lot. I was hoping for things like a Steel Challenge, where you could only use Steel types. Or best of all, I wanted to recreate the Little Cup
from Stadium 2 using the whole national 'dex.