DD's fav when little was mashed avocado/strawberry yogurt (lots of good fats!) I just mashed the avocado and stirred in some yogurt... offered the remaining "spread" to her in a dish with a spoon as well.
Haven't tried fish with DD yet (I am a vegetarian and fish is the only thing that makes my stomach turn!)
I haven't offered peanut butter either, but I do use a soy based "peanut" butter for DD that tastes very similar and has almost the exact same nutrition profile - it's called WowButter. She loves that too!
Like Anne, I cut DDs sammies into small bite sized pieces as well - still do most of the time as she tends to destroy them otherwise! Little bites are easy to pick up and eat without having to fuss with it much
