One thing I'm surprised to have seen only once is use of ¬ as an escape character, because it's so reliably unused for anything at all. (I noticed in the code that this program, which needless to say was written at a UK company, had no way of escaping ¬ itself, presumably because nobody had ever needed that.)
£ also seems a bit underused, but it's fairly specifically the UK's currency symbol, so it's not obvious else you'd use it for.
(But I suspect only UK keyboards have these chars, so it's probably no bad thing.)