I usually listen to full albums when I work, so I can't really put specific tracks' names, but well, I'd love to share too ^^
I mostly listen to OSTs so I'd say:
1. Shin Megami Tensei / Persona soundtracks
2. Anything composed by Kenji Kawai or Angelo Badalamenti
3. 1980s/1990s anime soundtracks (Dirty Pair, Cat's Eye, Card Captor Sakura, Utena - A LOT...)
4. Silent Hill soundtracks
5. Films noirs soundtracks (Naked Lunch, L.A. Confidential...)
If I want to listen to songs/singers/bands when working, I'll usually go with:
1. Sarah Vaughan
2. Hikaru Utada
3. 1980s J-pop and J-rock (REBECCA, Kahoru Kohiruimaki...)
4. Springtime Carnivore
5. Spice Girls over and over again xD
But when I really need to fully focus, I usually go to a nature sounds website (mixing rain with some birds and frogs), or on youtube to listen to the various tracks of a channel called Study Music ^^