The old desktop Korg tuners were solid and reliable. Their clip on models I have found to be fiddly (annoying) and flimsy (unforgivable). After my first AW2 fell to bits I bought another as it was the only one available (for 30 quid, b@st@rds) which now resides on a "stay at home" guitar held together with elastic bands.
+1 for Snark tuners, cheap, solid, effective.
Also GStrings free app for Android. All I need now is a piezo and a 3.5 jack for clip-on function.