I think mine are pretty obvious, but I'm gonna state them anyways:
1. MCV Evolution bodied MAN 14.240, the sleek body design, evolved from the Marshall Capital, which has been part of the majority of my life, combined with what is an absolutely gorgeous engine tone and ZF gearbox, just makes everything perfect, not to forget the amazing kickdown on AE09 DHM
2. DAF DB250 (preferably Euro 2 ALX400), these are my childhood, and are such beasts. I recently rediscovered my love for them at SEBF being able to ride both V347 DGT and X425 FGP, made me one of the happiest people on the planet. I honestly love these buses.
3. Euro 2 Dennis Dart, as Road-Hog stated above, all of those features combined, added with the beautiful, classic bodywork of the Plaxton Pointer 2, just ticks the box for me, I remember W334 VGX, which is now in preservation, Metrobus's last of the T33/353 batch. I used to absolutely love riding her after school when she showed up.
4. Euro 6 Enviro 200 with ZF AS-Tronic gearbox, I don't know why, but I love these, they're so full of character, the Electronic Manual Gearbox helps with this. and there is a "whoosh" noise that comes from ours, which I have no clue what it is, but I love it, especially when they thrash and overrev in 1st.
5. Scania N230UD Omnidekka, I believe we have the only N230UD Omnidekkas around (they are identified as they have the fatlip to prevent the horridly low door on N270UD and N94UD), and they have an amazing ZF sound on pull-away, and... just Scania. Top Notch.