Parkour and KitPvP, for sure. Both are super simple, and Parkour has so many maps, events, plots, etc to busy yourself with, I don't see how you could ever get bored of them all. KitPvP is pretty enjoyable to me right now, but that might be because I just started being active there, we'll have to see. I like the way kits are balanced compared to other KitPvP servers I've played.
I generally don't like PC Factions as it's too complicated compared to MCPE, and I don't want to spend 3 hours building, troubleshooting, and firing a cannon with such a high chance that the faction will intervene.
I haven't played Survival here so I don't know what it's like, but I tend to prefer single-player survival unless the server is a private SMP with friends.
Skyblock now is nowhere near as good as it used to be. I used to love playing it on a cracked server (not naming it) and on MCPE with my friends, but now Skyblock has gotten much more repetitive and much more competitive, rather than the casual minigames, PvP, discovery, and building that it used to be.
I'm thinking of playing Islands, because it's the first time I've seen a gamemode like it; it looks pretty interesting, to say the least.
I tried out Creative, but as I have creative plots on parkour and most of what I build is for parkour maps, I see no real reason to play Creative.