It is becoming more and more common for percussion instruments to be incorporated into a drum kit set up and we have notation to cover this.
Percussion is very useful in transcriptions that are arrangements of sampled parts.
The Tambourine
The tambourine is notated on the high E, in the top gap, where the high tom is also notated. It has a bolded 'x' for a note head.
Old Notation For The Tambourine
In some old drumscore.com drum sheet music, the tambourine is notated on the second ledger line below the stave with an 'x' for a note head. The intention was for it to be used as a substitute for the left foot hi hat, but I decided this was a silly idea. All transcriptions should now have been edited to have this notation removed but the odd one may have slipped through.
The Cowbell
The cowbell is a triangular note head. It can be pitched so is notated in a similar way to the toms. If multiple cowbells are used, the highest pitched will be at the top of the stave and the lowest pitched at the bottom.
The Shaker
The shaker is notated on the top line. It has an square note head. This notation is rarely used, but when it is the intention is for one stick to be put down and a shaker to be held instead.