Montserrat :( I remember learning about that in Geography. There is an actress Montserrat Lombard who was in 'Ashes to Ashes' but I really don't like it as a name.
I've always liked the look of Montserrat, but felt it was unusable. The "monster rat" thing never came to me, but I do think of Julian Serrat from the (short lived!) TV show Last Resort--he was kind of awful, so that mixed with "monster rat" gives it a pretty negative image. I definitely wouldn't use it for a FN, but maybe with the right FN it could work as a MN?
It is terrible.
If you love it, use it, but I recommend the middle only!
Montserrat is my youngest sister's name. She hates it. She calls herself Monster Rat and always yells at our dad for giving her a name that ends in rat. She's 13, so I find it all rather amusing (if it wasn't her name it would be something else) but she has a point. We call her Monse (we're Spanish speakers, so Monse is rather pretty), and nothing else. I happen to think the name sounds gorgeous in Spanish, which is probably why dad chose it. He doesn't speak fluent English and probably never even noticed the Monster Rat sound.