Most common Riichi Mahjong yaku. Sourced from http://tenhou.net/sc/prof.html

yaku.txt

- 44% Riichi (1h closed)
- 39% Yakuhai (1h open) - dragons/round wind/seat wind
- 22% Tanyao (1h open) - only 2-8
- 20% Pinfu (1h closed) - no triples/quads/yakuhai
- 18% Menzen Tsumo (1h closed)

- 6% Honitsu/Honiisou (2h open+) - One suit + honors
- 4% Iipeiko (1h closed) - same sequence twice
- 4% Sanshoku Doujun (1h open+) - same sequence in all 3 suits
- 3% Toitoi (2h open) - No sequences
- 3% Chiitoitsu (2h closed) - 7 pairs
- 2% Ittsu/Ikkitsuukan (1h open+) - the entire 1-9 sequence
- 1% Chanta  (1h open+) - All groups must contain 1/9/honor

- 0.9% Chinitsu/Chiniisou (5h open+) - all one suit no honors
- 0.7% Sanankou (2h open) - three closed triples/quads
- 0.6% Houtei Raoyui  (1h open) - ron on very last discard
- 0.4% Junchan (2h open+) - All groups contain terminal (+ 1 non-terminal anywhere, else Chinroutou)
- 0.3% Haitei Raoyue (1h open) - tsumo on very last draw
- 0.3% Rinshan Kaihou (1h open) - win by dead wall draw after kan
- 0.1% Shousangen - (2h open, effectively 4h) - Two dragon sets and a dragon pair