Political memes - not always; some are poignant or funny, but it irritates me when people constantly post them with 'Share if you agree' - if they feel that strongly about something they could take 5 minutes to express the view in their own words.
In particular, any meme that uses World War 2 to justify Brexit, unless the poster actually fought in that war, which is virtually never the case!
Any post that includes the lines 'I think only 5 (or however many) of my friends will care enough to copy this post; I think I know who they are'. Can't stand this sort of emotional blackmail, and it often spoils posts about genuinely important health issues, etc. Occasionally, I have indeed copied the post, but always with that bit taken out, and replaced by links to charities and organizations that deal with that health issue.
Coy posts and messages about breast cancer, which ask recipients to post something feminine, e.g. colour of your knickers!, and to keep secret why, and post only to female friends, etc. It's supposed to spread awareness, but if you're secretive about it, how does it spread awareness?! Also, I hate the implication that it's a purely female problem, as I've sadly known a man who died of it.