With three laws R’ Elazar ben Azarya was lenient and the chachamim were stringent.

1. Allowing a cow to wear an ornament between it’s horns in a public area on Shabbos.
2. To curry [combing an animal] an animal on Shabbos.
3. Grinding peppers in a small grinder on Shabbos.

R’ Yehuda says you can curry with a wooden comb on Yom Tov as it does make holes in the animal. The chachamim say you cannot even use a wooden comb.

Beitzah 2:9

A pepper grinder is made of three parts. The bottom bowl part even if made of wood can become tamai as it accepts things. The top grinding part, if made of wood cannot become tamai as it does not accept anything, but if it is metal it can become tamai. The sieve part which is made of cloth can become tamai, as any cloth can become tamai.