I've met
Dawn Fraser (Olympic swimming champion) met at Parliment house although she is not too nice.
Various former and current Australian rules football players, Michael Dipadomenico (Hawthorn backman in the 70's and 80's, multiple premiership player), Peter Daicos, better known as the Macedonian Marvel (Played for collingwood in the Late 70's, 80's and early 90's winning the 1990 flag). Mason Cox (Collingwood player (present day) the first and only American to play a senior game of AFL football and the tallest player to ever play a senior match of AFL football (212.5cm high), Lyndenn Dunn, Melbourne and Collingwood backman, I met him the day after he had a devastating knee injury and wished him the best of luck on his recovery.
Anthony Rocca a former dynamic midfielder for Sydney Swans and Collingwood, I met him at the time I got to go into the Collingwood rooms, he was a nice chap!
His brother Saverio Rocca is less famous in the AFL world but was still an amazing player for Collingwood and North Melbourne being the club leading goal kicker 8 times, a best and fairest, 780 goals, 2 ANZAC day medals. I met him at my Little Athletics Club where he attended when he was a kid, he still holds the record for the under 12 shot put and discuc. He presented my first ever medal. NFL fans might also be familiar with him as in 2008 he travelled to the USA and played games for Philidelphia and Washington.
Adam Treloar is a dynamic current player for Collingwood who used to play at GWS, he's quite nice a good midfielder and racks up 30 disposals a game! I also met up and coming backman Brayden Manyard.
I have also met plenty of players from the 2010 Collingwood Premiership side some of which are now retired, play for other teams, and some still play for Collingwood.
Those that I have met include
Darren Jolly
Dale 'Daisy' Thomas
Travis Cloke
Nick Maxwell
Luke Ball
Jaryd Blair
I have also met Hawthorn and Brisbane great four time premiership player, Luke Hodge.
As for Cricket Players unfortunately I have not had the chance to meet many though I have met Josh Hazelwood, a renowned Australian fast bowler.
Back to AFL I have also met and was given a tour of the Collingwood centre (Lexus/Holden centre) by Ash the head of tactics at the club.
I doubt anyone would recognize most of these people though.
EDIT: I forgot tennis players!!!!!!
Unfortunately I have not been able to meet my favorite, Roger Federer or my second favourite Rafael Nadal although i've seen Roger play and Rafa practice, but I have met Australian player and Grand Slam winner Samantha Stosur as well as the Italian, Andreas Seppi who I have cheered for against many Americans, Germans and French (i'm of italian descent so if an Italian is playing anyone except an Aussie I go for the Italian.)