You need to switch to a vocation that can use them. Note that none of the starting vocations are able to use them, you need to unlock the rest of the vocations, some of which can use Boomerangs.
The hexagoon
There are currently 6 DS Dragon Quest games. Dragon Quest IV - The Chapters of the Chosen Dragon Quest V - Hand of the Heavenly Bride Dragon Quest VI - Realms of Reverie (Revelation in the US) Dragon Quest IX - Sentinels of the Starry Sky Dragon Quest Monsters: Joker Dragon Quest Heroes - Rocket Slime
just keep trying
Use an Action Replay.
get the starflight exspress do story missions and grottos
Put on cat ears and then talk to the cat again. it will think another cat came to play with it.
At Zere take a diagonal left and at the purple acid go straight
After you complete the main quest, you can buy Falcon Blades from the weapon shop in Stornway.
there isn't a flying boat, but you can obtain a ship after completing the Bloomingdale story and the starflight express after completing a post-game quest
I believe you face freddy nine lives in chelsea court you have to have the quest from dworgyn. Once you talk to him back in nightside you learn animate.
axes, spears, shields, various armor. a lot of the things a warrior or other fighting classes can equip
the secret shop in dourbridge. you need the ultiment key which you get by killing goreham hogg. it's right beside the item shop.