After the bass drum I build the hi-hats. These are also based on the 808. I really like the fade switch. This can close the open hi hat when the closed one is hit or can leave it open, or somewhere in between. It has a great effect on the decay of the open hi hat. It takes external noise if you want to.
I’m a big fan of this hi-hat. the one think I would change is the panel color, because I like black panels more. Maybe I will change that in the future.
http://www.hexinverter.net/mutant-hihats
Difficulty to build: Medium to hard. Has multiple pcb’s and can take some time to build