Imo, having played Chipp since I started playing Slayer (so when I picked up GGXX), Chipp's Gamma Blade is only a threat because it can extend his combos. Outside of his knockdown into Gamma Blade, I've rarely ever seen it used by itself because on block it opens Chipp up to punishment. Even when not blocked, there's always a chance for a Slayer to IAD-j.HS, netting a CH into => death. Just for reference, although Gamma Blade is +5 on block, it has a 21 frame recovery animation, plenty of time to make him eat damage.
Instead, I'd have to say either 6P or 6H. I find Chipp's 6P to be rather subtle to notice, and like other 6P's, has upper body invincibility. As for 6H: it gives Chipp some very deceptive range, as well as potential to combo into some hard hitting damage.
I can't argue with running away, or c.s, since they're essentially core Chipp tactics. Teleportation and j.D and j.2k (I think it was the spinning kick downwards?) make for very nice mix up options.
Another note that I'd like to throw in is that Chipp has VERY limited overhead options, in the sense that all his overheads are extremely predictable and/or obvious. He has 6K (which is incredibly slow and easy to spot), 5D (comes out relatively fast, but still easy to block), 3rd hit of his Rekka chain (BBU'able), and for all purposes, leaf grab (counterable via 2P/5P). Thus I suggest blocking low, since his 2D and his 2K are lightning fast and can lead to damaging combos.
As for Slayer, 2S DOES NOT beat Chipp's j.D. I've found out the hard way. However, I have found, oddly enough, that 5P can either beat or clash with Chipp's j.D. But don't quote me on this, I've only managed to pull it off once in awhile. Blocking Chipp's j.D is a safe option.
I think that's about it. I'll summarize this post when I feel like it =)