[Clipper]

If you are talking about Powers from Super Munchkin and a few other sets (see the checklist in my signature), then that would be invalid. If you are just talking about a bunch of Items with powers (the game term is Bonus in this case), that's fine and quite common. There are limits for each type of card you can have in play and those are listed in the rules. Here are some of the common ones (note that most of these limits can be surpassed if you have an appropriate card):

Cards in your hand: Five at the end of your turn, but no limit at other times.
Race/Class/Mojo/Loyalty/Accent/Style/Training/etc.: One of each in play.
Powers: The total Rank of Powers that you have must not exceed your Level. If your Level lowers, you will need to discard Powers if you have too many.
Big Items: Can only carry one, so only one in play.
Steeds/Ships: Only one of each in play (and they carry themselves, so don;t count towards the Big limit)
Armor/Headgear/Footgear: You can have as many as you like in play, but you can only use one of each.
Hands Items: You can have as many as you like in play, but you can only use 2 Hands' worth.
Hirelings/Comrades/Mooks/Sidekicks/etc.: These are all the same type of thing and you can only have one of any kind in play.

The checklist in my signature also lists the limits for other card types.