OscilloScopen

http://www.allaboutcircuits.com/worksheets/scope1.html

Rigol DS1052E $350 

http://www.amazon.com/Rigol-DS1052E-Digital-Channels-sampling/dp/B003MYND5A

http://www.ebay.com/itm/All-New-RIGOL-DS1052E-Digital-Oscilloscope-50MHz-1G-/151499161374?_trksid=p2054897.l4275
Freaking awesome!
Supports triggering


$300 Siglent sDS1052DL (nice hardware, but crappy firmware ...not thought out very well)

http://www.amazon.com/Siglent-SDS1052DL-Digital-Oscilloscope-Frequency/dp/B00GQNN70A/ref=cm_cr_pr_product_top?ie=UTF8#product-description-iframe

BitScope $200

Small model which would show on the pi itself (basically allowing me to analyze the pi GPIO circuits  from the pi usb ....)

http://www.newark.com/bitscope/bitscope-micro/pc-based-oscilloscope-2-16ch-20mhz/dp/74X7819?MER=PPSO_N_C_EverywhereElse_None