Need a little old-school kick to start your weekend? Then look no further than SNK's developer page on the Play Store. Over the last few months they've populated it with no less than four of their classic Metal Slug side-scrollers (Metal Slugs 1, 2, 3, and X) and the top-down space shooter Blazing Star. All are available at significant discounts: half off for the Metal Slug games, bringing them to two bucks each, and a full two-thirds off for Blazing Star, which is now just a dollar.
If you've never heard of Metal Slug... well, shame on you. It started out in the Playstation era as a modern (for the time) arcade riff on Contra, featuring copious amounts of both running and gunning paired with crushing difficulty. In a unique spin for bullet hell shooters, your character will periodically jump in big honking tanks (the titular Metal Slugs) to turn the pixelated scenery into Swiss cheese. If you've only got enough dough for one, get Metal Slug X - it's an upgraded remake of the excellent second game. All four have added the ability to replay single levels.
Blazing Star is a well-regarded entry in the tried and true space shooter world, with some interesting additions, like ground enemies and multiple ships to choose from. Each one gets a screen-clearing special attack (of course) and surprisingly, there's also local multiplayer over Bluetooth. As with the Metal Slug games, levels can be replayed in the new Mission Mode. SNK has mentioned the sale on the various Play Store pages, but hasn't said how long the reduced prices will last - you might want to pick up these games sooner rather than later.