Grade II with one axe
Grade III with b2's and crampons (climbing partner has done IV 6 in b3's with b2 points)
IV 4 with a single rope, but i guess thats subjective to the route, we climb easy stuff in the alps with just one 1/2 rope and also stuff to grade III in the UK with just one 8.5mm rope.
In reply to An Triubhas:
B2 crampons are what exactly? Even C2 isn't really clearly defined. There isn't any difference in performance between the crampomatic G12/14 and newmatic G12/G14. Lets face it petzl dart are pretty similar to G14 in mono mode and will have been up some monster hard climbs (and certainly could be considered C2). If you are thinking of mountaineering crampons here they also wouldn't necessarily limit you at all on ice.
I've seen B2 boots with a proper toe welt before so perfectly capable of taking a newmatic G14.
1. About III though that was one of the all powerful nomics
2. Never used em but my mate who was seconding did perfectly fine on V 6 (ice)
3. VI 6 - big scary route on a decent sized mountain. A single beal joker.
Do you mean C2 crampons? If so then I think that tends to be the crampon of choice for many (the majority?). You don't need fully rigid crampons to get up hard routes.
The single axe is certainly the limiting factor here. Don't think I've climbed harder than II in this way.