I don't know where to start .. and I'm not sure if I should includet he solos either. Ah! I guess I'll do Top 15 just to be fair. (You'll know why in a bit XD)

Top 15
1 - Take me faraway - Ohno Solo [658]
2 - Song for me - Ohno Solo [308]
3 - Step and Go [265]
4 - Deep Sorrow - Ohno Solo [128]
5 - a Day in Our Life [98]
6 - Truth [93]
7 - Showflake [88]
8 - Kaze [81]
9 - PIKA★★NCHI DOUBLE [77]
10 - Touch Me Now - Sho Solo [75]
11 - Niji - Nino Solo [68]
12 - Hero [67]
13 - Carry on [64]
14 - CARNIVAL NIGHT part 2 [63]
15 - Still... [62]

Most of my stash of Arashi songs are played the same number of times because 'Shuffle' does wonders on my iPod, though I have to admit that I listen to the Ohno solos on repeat, even though I only have three that I really adore. (The three up there ^ XD)

oooh this seems interesting; it's fun to see what other people have on heavy rotation ^-^ i often reset my play counts :\ but here's the top 15 as of recent (i wont include the count)

1) Ohno - Song for me
2) a Day in Our Life
3) MatsuJun - Naked
4) Sho - Can't Let You Go
5) Ohno - TOP SECRET
6) Sho - Yume de mo ii kara
7) Ohno - Take Me Faraway
8) Nino - Niji
9) Aiba - Friendship (can you tell that i favor the solos? lol)
10) Step & Go
11) COOL & SOUL
12) Flashback
13) Aiba - Hello Goodbye
14) Nino - Gimmick Game
15) Dekirudake

it's usually on shuffle, but i favor most of these songs. hahah