This is a fairly exhaustive list of sushi ranked by (approximate) popularity in Japan. Western varieties are not listed (unless they happen to be popular in Japan).
1. Maguro NigiriThunnus Tuna (the cheap non-fatty type)
2. Kappa MakiCucumber — named after a Japanese monster (Kappa) who eats cucumbers.
3. Sake NigiriSalmon
4. Ikura GukanSalmon Roe
5. ToroFatty Bluefin Tuna belly
6. UniGonad of Sea urchin
7. AmaebiRaw shrimp
8. Ebi NigiriCooked shrimp
9. HamachiYoung Yellowtail
10. AnagoConger eel (saltwater eel)
11. Ika NigiriSquid
12. Hotate NigiriScallop
13. TamagoyakiFried egg
14. Tako NigiriOctopus
15. TaiSeabream Snapper
16. AjiJapanese Jack Mackerel
17. TekkamakiTuna thin roll
19. California RollOne of the rare types of Western sushi that's popular in Japan. A roll made of cucumber, imitation crab, and avocado.
20. FutomakiA thick roll containing multiple ingredients. Common ingredients include egg, kanpyo, cucumber and mushrooms.
21. UnagiFreshwater eel broiled with a sweet sauce.
23. Natto MakiFermented soybeans
24. SanmaMackerel pike
25. NegitoroChives and fatty Bluefin tuna belly
26. Kani NigiriCrab leg (real)
27. Kamaboko KaniFake crab (this is often called kani nigiri outside Japan)
28. UmeboshiPickled ume fruits
29. Shako NigiriMantis shrimp
30. Daikon Oshinko MakiJapanese radish pickles
31. AnkimoMonkfish liver
32. MentaikoPollock roe
33. TemakiA cone-shaped sushi wrapped in nori that's intended to be eaten with your hands.