The bike appears to be a low cost mass-manufactured bike sometimes termed a bike-shaped-object (BSO).
- rear wheel appears to have single wall steel rim.
- stamped steel derailleurs
- stamped, riveted chainrings with integral plastic protector
- oversized, 'looks cool' frame tubes, mig welds indicate thick wall metal
- non-adjustable shock absorber fork
- lawyer tabs on front wheel
- integral quill stem
- low cost grip shifters
- all of those reflectors
The front wheel looks like it may be double wall aluminum, it doesn't have the obligatory wheel reflector found on big box store bikes.
Pacific Cycles is a likely source, they make bikes under about 20 nameplates, including Roadmaster, Mongoose, and Schwinn. They also make short lived 'custom' brands; for a while they were offering a GM branded series at Wal-Mart. Finding an exact year and model name may be difficult because components would be shared between different name plates.
It looks like it's been well cared for, and if it's working for your riding habits you shouldn't have any trouble finding spare parts, especially if you've got a community bike shop around. Any big box store bike could be used to scavenge parts to replace those on this one. You could upgrade some components as they fail, but the weight of the frame and some limiting factors like the head tube would prevent you from upgrading it one piece at a time to bike shop components.