(Welsh) (and from memory) :- Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch. I learnt to spell this as a kid and have never forgotten it means something like: St Mary's Church in the hollow of the white hazel near to the fast whirlpool and the Church of St Tysilio of the red cave. Actually invented when the railway got there 150 yrs ago to give it the longest place name.
Supercalifragilisticexpialidocious another useless word I learnt to spell as a kid and still remember. Can't remember where I put my glasses though!