Atom Zombie Smasher [Steam store page]
Fairly easy on default, yet nearly impossible to win without using the chooser or combatant modifier - since it often gives you a poor selection of mercenaries. The balance could use a bit of work, since chooser lets you faceroll - but overall fun.

The Long Journey Home [Steam store page]
The RPG elements of this game are really well done - exploring the galaxy, meeting and interacting with other races, finding random items and trading them, or showing them to alien races in an attempt to discover what they do.

But the lander mini-game to harvest resources to repair and refuel your ship is more of a nuisance than a pleasure. It's fairly challenging to get right at first, but once you get used to it there are still planets where you come in way too hot and get unavoidably damaged due to the gravity or terrain. And even once you're good at it, it isn't enjoyable, just a chore.

So while a segment of the game is good, there's far too much of the rote lander upkeep missions to make the entire experience appealing to me.

Infectonator : Survivors [Steam store page]
The game concept/design is solid - scavenge supplies, rebuild your base, try to rebuild the car to get out of town - but there are a couple fatal flaws that really hurt the gameplay.

The main one is the AI - it's dumb as a box of rocks, and will walk through toxic slime (which kills the character in a few seconds) without hesitation, even when there's an easy path around it. Most of my damage and deaths in this game were due to the AI making stupid decisions.

And when a character "dies", they can be revived for around 15 seconds - which is fine except that it takes like 7 seconds to actually revive them. The timer doesn't stop as you're reviving, which means that if you get to the character with 3 seconds left on their timer, there's no chance you can save them.

It makes it frustrating if you're in the middle of fighting zombies and can't start healing immediately. I'm sure there are upgrades to make heals faster, but it's still a flawed design.

Just Get Through [Steam store page]
If you mash together the responsiveness of Super Meat Boy, and the randomness of Spelunky, you get a simple but satisfying randomized platformer.

Space Pirates and Zombies [Steam store page]
Slow but solid gameplay, though there are some major balance/difficulty issues - and to counteract those you need to grind quite a bit. The graphics are similar to a space RTS, though you have far less units than a normal RTS.

The Binding of Isaac [Steam store page]
Decent mechanics but disgusting theme. Enemies can shoot diagonally, you can't. The bad hit-boxes on arrows are frustrating, making yours regularly miss enemies and allowing enemies to occasionally hit you through walls. Made with Flash, low res.