Interest Rate Reserves - If using floating rate debt, this is the delta between your going in rate and your interest rate cap during the capped period. If you don't end up needing it you can give it back at the end.
Rate Cap Reserves - If using floating rate debt and you need to start escrowing for a rate cap extension in year 2, you could choose to raise what you think it will be on the front end knowing it can change on the backend. Pricing is tied to fed behavior, cap length, notional (loan amount) and interest rate volatility. Again if you sell early enough, you can just give this back to the investors.
Capex Contingency - This is a portion of your capex allocated for cost overruns or other unexpected capex (there is almost always something unexpected that pops up). This might range from 15-20% of your capex budget depending on property size/deferred maintenance.
Operating Expense Reserves - Having a healthy reserve here should be at least 1.5-2 months worth of operating expenses or the insurance deductible, whichever is greater.
Replacement Reserves - Typically escrowed by the lender and designed to cover replacing HVAC units, appliances, etc...
These are by no means hard and fast rule and some people overlap certain reserves. Healthy reserves can help to protect you and your investors from capital calls. What do you like to do differently?