Sample Lab (link to mini-review) is having a sale bringing the price down from $7 to $2! Thanks to reader hoyas79 for pointing this out! $2 is a really nice deal on a good sampler-sequencer. It has some flaws, but it is fun.

Buy Sample Lab on iTunes: $1.99 (On Sale, from $6.99)

Here's an example of the developer having fun with it.