I recently got the following in my server logs:
70.190.xxx.xx - - [26/Sep/2010:19:03:17 -0500] "\xdcm5\xa1\x1a\xec\xa2\x7f\xc2\xab\x83<\xb5\xa3h\xb1^B\x88\x19K\xa5C\xcf\x15\x1a\xc1\x84\xe4\x8a]c\xdd\xe0\xc2e\x9f\x7f;M\xa0P\xfb\x8bo\xf6\xcb\x12\xdaq\x81\xb7\xf6\xe3N\xb5\x04`\"\\xcc" 200 4581 "-" "-"
and
70.190.xxx.xx - - [26/Sep/2010:19:10:54 -0500] "&\x9a\x18\x02\xef@2s;\xff\xea\x84" 200 4582 "-" "-"
Normally I wouldn't be concerned because I do get a lot of junk randomly hitting my server, but I've never seen anything like this one and the server is returning 200.