FLCL is an amazing anime. It's also an anime that can be easily dismissed; it's crazy, manic, colourful and bizarre. However, give it a chance–and possibly a few repeat viewings–and you'll discover one of the deepest six-episode OAVs you're likely to find.
Even if you don't want to look beneath the craziness, this is still an enormously entertaining piece of work. It has fantastic, memorable characters, a crazy sense of humour and a wicked subversive edge. Also robots and vespers.
One of my all-time favourite anime–heck, one of my favourite ANYthings–I highly recommend FLCL, both for the casual lover of wackiness and for those wanting something deeper.