I beg to differ - not a wireless one! It may show spurious results when batteries become low.
There's really nothing special necessary in a game where the left click pulls the trigger. For me,
1) wired!!!
2) fitting to my index finger,
3) between unexpensive and outright cheap.
I have two really small ones from those notebook gadget sets - they are great!
This is one of them, 3" x 1.3"