The Staedtler Triplus
The Triplus is the fineliner journallers keep coming back to. A 0.3mm metal-clad tip holds its point through heavy use. The triangular barrel sits well in tired fingers during long writing sessions. Ink dries quickly enough to avoid smudging for most left-handers, and the colours stay true page after page. The ventilated cap means leaving it uncapped for a few hours does not ruin the tip.
Uni Pin fineliners
The Uni Pin is the archival choice. Waterproof, pigment-based ink that is lightfast and will not smear under a wash of watercolour. Available in 0.03, 0.05, 0.1, 0.2, 0.3, 0.5 and 0.8mm. For journallers who also sketch, or who worry about longevity, this is the one.
Paper matters
Fineliners that bleed on cheap 70gsm paper may be perfectly clean on 90gsm or above. If you are using a cheap spiral-bound notebook and finding bleed-through, the answer is often better paper rather than a different pen. The Staedtler Triplus is among the most forgiving on lower-quality paper.
Colour range
If colour is your priority (calligraphers, bullet journallers doing colour-coded pages), look at the full Triplus range (over 40 colours) or the Stabilo Point 88 (over 30). Both are available as sets and as individual colours for refilling specific shades.