When B. Andrew Barta founded Tech 21 in 1989, the company had only (albeit very popular) product, the original Sansamp guitar amplifier emulation pedal. Eventually, Tech 21 branched out and offered more Sansamp variations and even guitar amps. Not content to stop there, Barta and the Tech 21 crew also began manufacturing specialized overdrive and distortion pedals. Now, Tech 21 offers over twenty different pedals to suit a variety of different needs.
Of course, Tech 21 is renowned for their warm analog amplifier emulation, so there's no shortage of amplifier-based pedals. While the original Sansamp Classic is currently discontinued, Tech 21 still offers the GT2 Sansamp, capable of emulating classic amplifiers using a variety of selectors. Recently, Tech 21 began offering direct emulation of specific amplifiers, known as the "Character series." These pedals, such as the "Leeds," the "Oxford," and the "British" allow you to emulate guitar amplifiers from a wide range of manufacturers such as Fender, Marshall, Vox, Hiwatt, and Mesa/Boogie.
Tech 21 has also recently forayed into other effects pedal types, such as chorus, reverb, and delay (in addition to other more traditional distortion and overdrive effects). Not content to merely copy, Tech 21 puts their own spin on these traditional effects. For example, the company's delay pedal - the Boost D.L.A. - focuses on analog warmth while also providing a slight signal boost to compensate for the volume drop in traditional delays. Very smart indeed!