Rudy uses a front facing mgn9c carriage, so any toolhead that supports that should work. You ideally want something that's as small on x and y as possible to not limit travel. If you are using limit switches, you also want to make sure that your toolhead can hit those.
The Warhead is a custom design specifically made for Rudy. It uses a V6 hotend with a 3010 fan and a 4010 blower for part cooling. Since it's not strictly a part of the Rudy project, it has its own repository and BOM, but if you purchace the Rudy BOM, you should have enough leftovers to build it too.
Pros:
- tiny, barely bigger than a V6
- prints quickly
- uses standard parts
Cons:
- in active development
- the part cooling is okay at best, this is being worked on
The Rookery is a very well designed toolhead from Gulsifer on the Rook discord. It uses the same mounting style as Rudy so it should work too.
Pros:
- much more mature design
- supports different hotends
Cons:
- default hardware is very weird, it uses both MK8 and Volcano parts
- slightly more expensive to source
- I personally am not convinced of its hotend cooling capability
- big, it will limit x and z travel
DDRudy is a direct drive toolhead custom-designed for the Rudy printer by @skillenmcnot. It is based off the Orbiter v2 extruder and the Trianglelabs CHC Mini hotend. Other hotend and extruder combinations are possible, although a different extruder may require moving the mounting hole positions in the model.
Pros:
- custom designed for Rudy
- supports different hotends and common replacement parts
- excellent cooling performance
- actively being improved
- editable model files available
Cons:
- requires a moderately well-calibrated machine to print properly
- wider than Warhead, it will limit x travel to 90mm
The Salad fork uses the same rail for x, and the modified the mini afterburner and the mini stealthburner from the voron 0 to fit that. While this is currently not officially supported on Rudy, i don't see any reason why it couldn't be used.