Merchant Limpwurt roots, dropped by Hobgoblins.
the most expensive: blue partyhat the most useful combat weapon: corrupt dragon scimitar
I think runescape is
world 57
Gravite shortbow.
The overall best f2p Runescape weapon is actually a range weapon - Maple Longbow (sighted). It has a range bonus of over 100. The best f2p degradeable weapon is the Gravite 2h. Both are Dungeonneering weapons and need 45 Dungeonneering levels.
For F2p it would be the Rune 2Hander as it has the highest str bonus, but i prefer the scimitar:D
XP- something like 10-20k
Nope :)
Steel Plate Bodys
As far as I know, no F2P item can do that. I'm not sure about P2P but it is highly unlikely without Prayer or other bonuses.
you can keep all your items but you can't use them in F2P.
The only f2p dragon is the one from the quest "dragon slayer".