Developer CAVE is looking to make it a bullet hell holiday for its fans by getting in on the year end sale bandwagon. CAVE just recently dropped Bug Princess [$4.99/Lite] into the App Store, a game which we liked a whole bunchwhen it released, and thought was quite reasonably priced to boot. Now, you can pick up all of their previous major iOS titles at a discounted rate from now until January 10th.
Espgaluda II HD, $13.99 → $10.99 (iPad 2 Only)
If you aren't sure about a purchase, each and every one of these games has a lite version you can check out, and there are even versions of Espgaluda II that are split into separate "Arcade" and "iPhone" standalone apps that are available for a cheaper price. Also, make sure you're equipped with at least 3rd generation hardware or above, and in the case of Espgaluda II HD, you'll need an iPad 2 specifically to run that bad boy.
At any rate, all of CAVE's games are high quality offerings worthy of your dollar, so be sure to hit up this sale while it lasts.