I want a nice ring3 linux x86 debugger. I'm not satisfied with current debuggers for linux. What do you say? anyone shares my idea?

The problem with all Linunx/BSD debuggers is that most of them (and gdb is prominent example here) had never been designed to debug assembly language - most are source level debuggers since whole system code is open source. Quite opposed to DOS/Windows platform which explains why those platform have many more better debuggers. The one assembly level debugger I'm using on Linux x86 systems is IDA Pro. So instead of writing a stand alone debugger I'd suggest implementing IDA Pro plugin to handle FASM symbols especially that at one point any serious asm developer will need to consider purchasing IDA.

isn't it a disassembler?
i've used ida once on windows it was awful.

IDA is not only a disassembler but also provides debugging capabilities for a number of platforms including Linux/x86. I agree that for novice user it may even look scary and the debugger interface is quite different from others but once you learn all the quirks and tricks it is the must have tool for serious assembly level debugging. The option of exchanging data from disassembler and debugger is a unique and powerful feature and if you add to it IDC, IDAPython and SDK functionality you have one great reversing/debugging framework.