Im a huge fan of the DOD 250 overdrive, regardless of the price. Its a criminally underrated and underappreciated pedal that responds very well to dynamics and playing style and is still one of the most transparent pedals on the market that doesn't use a clean blend.
This is probably one of the most cloned/modified circuits in effect history (To be fair, it also happens to be a modded version of the Distortion Plus). The circuit has been used in many pedals that get far more praise than the 250 ever seems to get.
The exact circuit is used as the main distortion stage of the original Klon, the Klon just adds a buffer for a cleaner signal and a tone stack for mid shaping. (Fairly easy mods to drop into the 250 if you DIY)
The Fulltone OCD "TB's Favorite" is literally just 2 DOD250's stacked into each-other with the clipping diodes removed from the second stage and a tone stack to adjust the mids.
The RAT and all of its counterparts are heavily based on the DOD250, just with some tweaks to allow for more gain and tone shaping.
You can often find the 250 online for around $40.
(If you DIY, For some added flexibility, these pedals really benefit from adding a BMP tone stack to the output of the pedal. Its a simple DIY mod that takes a couple minutes to finish, but really makes the pedal come to life on the bass... If you really want to get fancy, you can even add a clean blend)