This is a fun topic. Also a tough one, since most worthwhile indie games land in the $14.99-24.99 range.
Wizorb - $4.99
An entertaining little role-playing adventure using Breakout/Arkanoid mechanics
MagiCat - $4.99
A charming throwback action-platformer with high replay value
Gato Roboto - $7.99
A solid Metroidvania held back only by its short running time.