Waunarlwydd, a well-performed fifth in the League table, led the Division 2 East side 34-20 with only 10 minutes left on the clock, but Abercynon produced three converted tries to steal it. Waunarlwydd out-scored the visitors six tries to five, with centre Ricky Price bagging two, but Abercynon inside centre Matthew Turner proved the difference with seven goals, including all five conversions.
Llanharan produced the biggest win of the Division sides - a 94-5 mauling of Division 4 West club Crymych. Twelve of Llanharan's 14 tries were scored by backs - including a hat-trick to fullback Arwel Davies - while outside-half Greg Jones banged over 12 conversions. Winger Rhodri Thomas scored to make sure Crymych weren't "nilled".
As expected, runaway Division One leaders Bonymaen continued their perfect start to the season with a 76-0 shutout of Division 3 West club Newcastle Emlyn. Nine Bonymaen players were on the score-sheet, with outside-half Gareth Jones adding a try to his 21 points with the boot.
Blackwood eased past Nelson 47-15, with left winger David James dotting down three times, while Whitland returned from Porth with a 31-10 victory.
Former Premiership side Caerphilly retained their unbeaten home record with a 64-22 win against Division 3 East side Blaina. The visitors were brave in defeat, scoring four tries, but were always behind as the Cheesemen ran in 10 of their own.
Narberth had no problems with Vardre, running in nine tries in a 59-15 win. Centre Steve Martin scored three of them, with fullback Matthew Davies adding a brace.
UWIC winger George Dixon produced the most impressive individual performance of the day - running in five tries in the Students' 50-24 win over Brecon - while Ystrad Rhondda beat Glyncoch 23-10.
Bottom-placed Fleur de Lys recorded their first win of the season, and the players didn't even have to get out of bed as Chepstow decided not to turn up. Builth Wells also won in a walkover when Abercrave failed to raise a front-row.
In the other matches involving Division One clubs, Cymllynfell won 35-7 at Loughor, Merthyr returned from Penarth with a 57-16 victory, Llangennech won 27-3 at Pentyrch and Beddau beat Gilfach Goch 26-3.
Further down the divisions, Cardiff HSOB winger Gareth Jones scored three tries in his club's 53-0 shutout of North Walians Dolgellau, while Llantwit Fardre ran in eight tries in a 46-7 victory over Llanelli Wanderers.
Division 5 East side Machen produced one of the major upsets of the day, battering Division 3 South-West club Tondu 36-6. The home side led 17-6 at the break and never looked like losing. Mountain Ash fullback Dale Keepin scored four tries in a 54-24 win over Caernarfon, while Newport Saracens winger Lewis Culverwell scored twice in their 36-0 win over Gowerton.
Pill Harriers prop Mark James is in danger of getting kicked out of the Frontrowers' Union after scoring a hat-trick of tries in a 29-15 win over Abergavenny, while Pencoed centre Gareth Jones scored four tries in a 40-7 win over Nantyglo.