Saeviomagy
Adventurer
If you aren't a rogue, you probably want something better than a dagger.
The interesting thing is that this is NOT a restriction that relies on rogue powers being limited as to what weapons they allow. It is in fact primarily reliant on the fact that rogues are given a bonus with the dagger and have a large non-weapon related damage bonus. There's a feat which allows you to pick up a heavy blade and use that, and charop recommend NOT BOTHERING because light blades have excellent support and turn out to be better for a rogue to use.
Now sure, if you had full rogue abilities with a gouge, that might cause issues.
However the current rules on rogue abilities and powers cause some issues in and of themselves. For instance rogues cannot strangle someone with a piano wire. Why? Piano wire is an improvised weapon. Improvised weapons are not a light blade, crossbow or sling. Therefore NO rogue powers work with piano wires, including garrote grip. Amusingly enough, you cannot knockout someone with a blackjack (without a very specific and awful rogue build).
In fact, even jumping through hoops, the most current rogue errata (playtest, whatever) makes it impossible to garrote grip with a garrote EVEN IF you take the garrote line of feats to make a garrote a light blade, because some genius decided that garrote grip should require one free hand.
The rogue powers don't need weapon restrictions to be balanced. Only sneak attack actually requires that. But someone thought it would be evocative and flavoursome to limit their use and so we're left with a bit of a trainwreck.