My most regularly used #fountainpens, in order of regularity of use:
1. Kaweco Liliput, copper, extra fine steel nib
2. Pilot Lady, extra fine gold nib
3. Pilot Custom Heritage 912, FA nib, aftermarket ebonite feed
The Kaweco will go months without drying out and can live in my jeans pocket. The 912 is big and thirsty and that's why I'll more often grab the Lady for longer writing sessions.