Does historical count here? If so there are quite a few...
A personal favourite of mine were the early-00s Wales & Borders services in/out of London Waterloo.
One was a 0753 from Manchester Piccadilly (0703 Saturdays) which ran via Shrewsbury, Hereford and Cwmbran to Bristol Temple Meads, then up through Bath, Warminster and Woking to arrive in London some 6 hours later (1406/1314). The return working left Waterloo at 1517 weekdays (1417 Saturdays), arriving back in Manchester at 2138/2025.
An overnight weekday working originated in Pembroke Dock at 2016 and ran via Swansea, Cardiff and Bristol Temple Meads, reaching London Waterloo at 0427. Not sure if the idea of this was a ferry connection, to offer an early connection with Eurostar, or maybe a bit of both. The return working left Waterloo at 0505 and ran back via Bath, Bristol and Cardiff to Bridgend, where it continued to Maesteg, arriving at 0911.
Elsewhere, around the same sort of era...
I seem to recall Central Trains had some weird and wonderful connections during their time, with Aberystwyth as an example seeing destinations such as Lincoln/Grimsby and Stansted Airport.
Then less distance admittedly, but the short-lived London Crosslink service operated by Anglia Railways saw them leave their home turf at Stratford, then venture through - and stop at some - north London and Surrey commuter stations, to reach the Hampshire town of Basingstoke.