Mountain Bikes

Hardtail vs. full-suspension is the first real decision. Sub-$1,000 hardtails (Mongoose Status, Schwinn S29, Huffy Marker) trade weight and component quality for price — usually 32–36 lb steel or low-spec aluminum frames with mechanical disc brakes and Tourney-tier drivetrains. Full-suspension MTBs under $1,000 are largely marketing; meaningful full-suspension starts around $1,500 because the rear shock and pivot hardware cost real money.
What actually matters at the budget end:

Hydraulic disc brakes, not mechanical. Mechanical disc brakes require constant adjustment and lose stopping power as cables stretch. Hydraulic is the upgrade most worth paying for.
Shimano Altus or better. Avoid Tourney-tier drivetrains if you’ll ride more than once a month — the shifting degrades quickly.
27.5″ or 29″ wheels. 26″ wheels are being phased out for adult bikes; 29″ rolls over obstacles better, 27.5″ is more maneuverable on tight trails.
Aluminum frame, not steel. Steel adds 4–7 lbs to a hardtail at this price point.

Featured reviews: Cybic 26″ Mountain Bike, Schwinn S29, Schwinn Traxion, GT Avalanche, Mongoose Status, Mongoose Malus, Pacific Mountain Sport.
For commercial guides see best budget mountain bikes and best mountain bikes under $1000.