From this Language Hat post:
Colon "part of the large intestine" and colon "punctuation mark" are both from Greek, but from different original words. Similarly, coma "cloud of gas and dust around a comet" and coma "state of unconsciousness" are also both from Greek, again from different original words. (Read the post for details.)
Fun stuff, that.
(False friends are also fun, such as the "much (en), mucho (es)" pair mentioned in the comments to that post, or "haben (de), habere (la)".)