@fba827: I mean, if we can use implements to attack (physically) without being houseruled. XD But you gave me both infos so I have extra info now. Thanks. XD
@Scalding: So there are implements that are weapons? (not wands, staves, rods, etc)
@DracoSuave: ahh, so Implements are actually used to attack. XD Thanks for the info.
Implements are exactly analogous to weapons. If you have a power with a weapon keyword you MAY use a weapon with it. You don't HAVE to, you can use a weapon based power without a weapon, but in that case it defaults to being an 'unarmed' attack. If you have an implement keyword power you MAY use an implement with it. You don't HAVE to, you can use an implement power with no implement at all.
There are some minor differences between the two types. A weapon attack (almost) always uses the "W" of the weapon to determine damage, implements don't have a "W" value, instead the power itself defines the damage dice. If you use a weapon power without a weapon then you simply use the unarmed "weapon" instead, which defines the W value as 1d4.
There are other differences:
1) All weapons, except "unarmed" have a proficiency bonus that is applied (unless you attack with a weapon you aren't proficient with). Implements don't have a proficiency bonus.
2) Different feats apply to weapons and implements. Weapon Expertise applies to weapon attacks using a weapon you have expertise with. Implement Expertise applies to implement attacks using an implement you have expertise with.
3) Some weapon attacks use missile weapons or "ranged" weapons, in those cases the weapon determines the range of the power for that attack. Implements don't have ranges, instead ranged implement powers have built-in ranges. There are some minor exceptions to this, it is possible for instance for a weapon power to have a fixed range and there are some bard (artificer as well I think) powers that can pick up the range of weapon they're used with.
As DS said there are weapons which can be used as implements. In those cases weapon oriented feats usually apply to the attack, like weapon focus even though its an implement keyword power. Various ways exist to make this happen, as DS already outlined. Staff implements also are usable as weapons (quarter staff), which works pretty much the same way.
There are a few other minor points. PHB3 introduced superior implements. These are non-magical implements that have enhanced properties. Implement users can use the Superior Implement Proficiency feat to allow use of these. There are a number of types, but they all enhance implement powers cast using them in some fashion. All of these work essentially the same way as normal implements.
As others have said, you probably can use an implement as an improvised weapon. In this case though its simply the same as using a rock or a stick. There's nothing special about it, you're just bashing the orc over the head with your orb or whatever. Its slightly better in some cases than an unarmed attack, but not much.