im assassination spec but i might switch to combat should i use 2 maces a sword and a mace a dagger in the main hand and a mace or sword or 2 swords.

Combat usually requires 2 of the same type of weapon,
The main hand being slower, 2secs+ and the offhand beging faster, 1.5secs-ish faster offhand = more spell pushback and
much better application of stackable poisons

Seeing as you can change weapons while your fighting get a fast offhand weapon to push back spellcasting then get a main hand dagger and a slow main hand weapon so in all you will have 3 weapons two for the mainhand and and fast offhand weapon. Then replace the moves on your actionbar for moves such as sinister strike as hemorrhage with macros as follows,

/equip [slow weapon name]
/cast sinister strike

or

/equip [slow weapon name]
/cast hemorrhage

depending on what spec you are.

Then for moves that require daggers such as backstab, mutilate or ambush replace the backstab, mutilate, ambush moves on your actionbar with macros as follows,

/equip [dagger name]
/cast [backstab]

or

/equip [dagger name]
/cast mutilate

or

/equip [dagger name]
/cast ambush

therefore everytime you need to use an ability that requires daggers it will switch to your dagger and use the ability, and everytime you need to use an ability that will do more damage with a slow weapon it will switch to your slow weapon then use the ability.     
I would suggest that for the macros you use the same picture as the one on the ability you are replacing it with so as not to confuse yourself.