Wizards, warlocks, and artificers, actually. Artificers (and bards) also have a bunch of weapon attacks where you don't need to worry about implements, which makes them more attractive for multiclassing. And of course you can always take AIP to combine all of your arcane spells under one item (make it a blade and gain extra flexibility in being able to use weapon attacks with your primary weapon).Flavourwise, A Bard/Druid is very viable. Yet mechanically they are at a disadvantage with regard to implements. The bard is going to have this problem every time he multiclasses into anything except Wizard (as they use Wands).
This is really annoying in the character builder; even if you can use the implement in question (say, half-elf feylock takes a bard implement at-will with dilettante), it won't work with the racial power unless you have the multiclass feat.Also the Half-Elf Dilettante power is inferior chosing any implement power from a class that the player doesn't intend to multiclass into.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.