My friends and I were planning a game and we all decided we wanted it to be a lycanthropy campaign. One of my friends had already made his character (a halfling druid) before this decision was made. He doesn't want to change his race so He's trying to pick a good base animal. Any advice?
I'd pick a cat type honestly.
Something like a were-bobcat.
Or a were-tiger.
Don't be afraid to downsize the animal stats, if he was a natural born, then he could really be whatever one of his parents was.
Even if one was a human and one was a halfling, you could still have a were-bear halfling, just.... smaller.
Were-teddy bear?
Wererabbit is quite correct thematically, or wereweasel/ferret/stoat. Weremagpie would fit beautifully. Weredog or werecat too. However... Think bigger. A weremoose or werebison would be simply perfect. If you go aquatic, you can't do better than werecachalot.