Diabolic Skeletons by the hundreds, one dragon

You play a knight cutting through a land the monsters have overrun. The combat is simple to pick up: sword, bow or fireballs, and enemies that come at you in waves. A few keys and the mouse is all it takes. The monsters mob you, and getting through a packed room is where the game is at its best. Some enemies freeze for a moment when hit, so with enough damage you can wipe a whole group without moving. Levels are hand-built rather than random, so you learn where each spawn sits and how to handle it. The difficulty climbs steadily, and the final levels push back hard.

There are no classes. Gold from chests and kills buys skill points, and you split them across four branches: your hero's health and speed, sword skills like vampirism, magic attack and regeneration, or archery with poison and arrow recovery. Tank, spellslinger or archer, it is your call, and if a build turns out wrong you can reset your points and spend them differently. One honest note: the last levels ask for heavily upgraded attack skills, so expect to replay a stage or two to afford them. Come for the fighting and the levels more than the endgame balance.