As you surely know, you get some items by going a lot of times to certain places, this is the list of items I've gotten so far:
Park History Book: go to the park 50 times.
Dart set: at Game Center play Darts 40 times.
Billiard balls: at Game Center play billiard 40 times.
Portable Game: go to the Electronics Store 50 times.
CD box: go to the CD store 50 times.
DVD box: go to the Anime store 50? times. (Not sure of this, it was the first I got and I wasn't counting)
Maid Uniform: go to the Maid Cafe 50 times.
Skate boots: at the Sports Center skate 40 times.
Squash racket: at Sports Center play squash 40 times.
Training Set: at Sports Center go to the gym 40 times.
Homerun Ball: at Event Hall watch the baseball match 30 times.
Doujinshi: at Event Hall attend to Comic Basket (lol
) 30 times.
Classic CD set: at Event Hall watch the classic music concert 30 times.
Idol Fan: at Event Hall watch the Idols Show 30 times.
Romantic Novel: go to cinema (romantic movie) 30 times.
Toy Gun: go to cinema (action movie) 30 times.
Spaceship model: go to cinema (sci-fi movie) 30 times.
Anatomy model: go to cinema (horror movie) 30 times.
Anime figurine: go to cinema (anime movie) 30 times.
If you know how to get another items post it here.
EDIT: added some more items.