not sure if I can find 10, but here I go:

1) EG.r craft design and logo design. all the other ship designs and team logos, as well as the F9000 league logo I thought were pretty uninspired, but EG.r had something cool about them.
2) Florion Heights 3, forward and reverse. Forward had this absolutely lovely jump at the end, and reverse had the same jump turned into a very cool climb, followed by a wonderful long sweep downhill. Also Florion Heights was one of very few tracks with a rather well-made open section.
3) Missile rear lock-on. Oh how I would love to have that on xLink
4) The setting of Alca Vexus. Valparaiso was one of my favorite 2097 tracks, jungle and stuff, so I really dig the Inca-temple/jungle setting of Alca Vexus. The tracks there were some of the best in fusion, too.
5) Papua New Guinea. I know this has been mentioned before, but you just have to adore how great this song is.
6) Sections of tracks with no rails on either side. Fusion introduced them to the series, and I am glad they kept them for purE.
7) Custom League - most important new idea! I wish it was possible in purE, and I sure hope it will be in the next (online) wipEout!
8 )Transparent pieces of track. Would be especially cool on tracks like Sol2, then you could see people passing under/over you!
9) The open section on Vohl Square 3. Maybe not really fitting for a wipEout game, but it just felt cool, very gritty and chaotic.
10) ...man, now I am running out of things to like about Fusion... uuuuuhm, oh yes! Almost forgot! The extra cool animation before the start showing how the ships would come up from the hangars below the grid! I was wowed first time I saw it! Please bring that back for the next wipEout!

well, well, there ya have it