A Digitech Trio Band Creator is a lot of fun, particularly if you just want to rehearse. It is an artificial '3 piece band in a box' where the backing bass and drums are created electronically to your loaded riff.

Load a riff into it with a clean signal from your guitar and it plays back a bass guitar and drums to your riff. You can load 3 riffs and switch between them (higher model can hold 5 riffs), and there are controls to set the tempo of the playback speed and there are a variety of styles to choose from.
As an example, say you load in a basic 12 bar as riff 1, and a suitable bridge or middle 8 as riff 2, then when played back in the 'Rock' setting you find it boring or old hat, well without reloading you can change the Genre style to Blues or Jazz or Alt Rock or R&B or Pop or Country, and then set the tempo and "Alt timing" as you desire.
It has a separate outputs for the bass/drums and guitar, or you can use it as a single combined signal to an amp. A headphones socket for 'silent' practice. There are two models and the higher priced version includes a standard style guitar looper to the electronically generated bass and drums backing band

I don't use my cheaper model as often as I should, but it is a lot of fun and can challenge your creativity and your dexterity (being that the electronic bassist and drummer NEVER tire or drift in their timing or loose their patience with you).