In Saffron City
If you're talking about Starter Pokemon, Steven gives one of the Hoenn starters (Treecko, Torchic, and Mudkip). He'll also trade his Beldum for a Forretress. You also talk to him in order to allow Latios/Latias to enter the game.
he gives you beldum, a Pokemon from hoenn. you can't catch beldum from hoenn in jonto or kanto so don't refuse the offer!
Steven doesn't give you a pickaxe, but he gives you a Beldum...
He returns to silf co. after about a month and offers to trade his Beldum for a foretress
professor elm gives it to you
steven gives it to you in mossdeepp
In Pokemon Emerald, when you complete the Hoenn Pokedex, Proffesor Birch gives you a Johto starter. In Pokemon HeartGold and SoulSilver, after defeating Red, Professor Oak will give you a Kanto Starter and Steven will give you a Hoenn Starter.
a guy running out of mt.mortar gives it to you
Steven gives it to you on the bridge to the west of Fortree City.
you pick a squirtle from the Pokemon proffeser oak gives you to choose from
you need the enigma stone and go to the museum and talk with the guy what gives you Pokemon from fossils and go outside and a latios appear in heart gold and a latias in soul silver, you can get this item in a Pokemon event or with action replay
In Mossdeep City, Steven gives it to you.