One that I just came across recently:
Witches, excellent for armies.
1) Take a Witch with the Fortune and Cackle hexes; possible at 1st level with the Extra Hex feat.
2) Gather as big a group as you want, that will fit in a 30' radius.
3) Use Fortune on them, one at a time, using Cackle each round so none of that expires.
4) Now just use both actions to Cackle for however long - let's say eight hours.
5) The Fortune buff now lasts for however long you Cackled, beyond when you stopped Cackling. So if that was eight hours, the group now has eight more hours to kick ass.
6) But wait - it gets even better. Cackle extends the duration of any Fortune effect, not just one you created personally. So with multiple Witches, you can extend the duration a lot more.
7) For example, if ten (1st level) Witches spend an hour, the Fortune effect will last for 19 hours! Or if those same Witches spent eight hours, it would last for 144 hours (6 days)!
This applies to the negative hexes too, but you'd need to have the victim restrained/asleep/whatever, so you could just CdG them instead. But if you're very spiteful, you can give someone a temporary pseudo-curse that's hard (maybe impossible) to get rid of. Might be useful for Charm, in fact.
Shaman can do this too, if you want to be more dignified about it (chanting instead of cackling). But they do need to be a level higher.