I know it specifies Z but i have to start from beginning.
Dragon Ball saga Favourite chars and why:
Son Goku from start to end and not because he is destine to be the ssj4 but thanks to his polite, fun and innocent behavior that gives me a good laugh at everytime i watch at him.
Muten the old perv yes, he can be a real perv most of the time but when the needs call he doesnt back off. Full power kamehameha is just fabulous done by him. And he too is funny.
Karin for .. everything ?
The other chars go equally with each other but wont match those 3 for me.
Goku , even if slightly less than in the original saga, i like his power ups, training styles, fighting techs and... POTARA FTW.
Vegeta is the anti hero yeah but his being stubborn gives him an odd fashion not to mention his forever behaviour of the -Prince of the Saya jins- and... POTARA FTW.
Trunks from future has his past as background and gives him a good lore and look if you check his motivations.. and he is not as whimpy as the actual trunks.
Gohan vs Cell .. you'd ask me why not just Gohan ? Because Gohan vs cell is 1 thing and gohan before and after cell are different things. Gohan Ssj2 Kamehameha plus Goku its just wonderful, makes me sad that im not gay during those times.
Fat Boo .. well he is funny as hell isnt he ?
DB GT :
Goku again but less , if it wasnt for Baby's fight i wouldnt even put him here actually since he is totally annoying before that. During the fight with super c17 he does few mistakes like charging him with a kamehameha x10 but he makes up for it later so i forgive him. And against Shenlong ... Gogeta's Big Bang Kamehameha says all.
I'd say Vegeta here too but his role is too little apart from giving Baby a body and the fusion with Goku.
Favourite times in all DBs ?
Second tournament Goku's takes part in. DB 1
Cell's Game. DBZ
Shenlong's fight. DBGT